Test Equipment Anonymous (TEA) group therapy thread

[Specmaster]

@Vince, I'd also give those boards a thorough scrub and clean up as well when you get the correct bits back in so that when you photograph it ready for sale, it will really look its been meticuleslly cared for and repaired proffesionally, it will reward you with a better valuation by buyers. 

[Vince]

Yes Spec, I was thinking exactly the same !
As soon as it's fixed, a good wash will be on order 

These boards look really horrible....

[Neomys Sapiens]

Yes, so many trimmers and the one time I really need one... I can't find the correct one ! 

I think I need to do some more component sorting and inventorying... need to inventory all these trimmers so I know what I need to buy to fill the gaps.

And some 10K 1/4W resistors as well...

With hindsight, I'm not surprised. As I tinkered a lot with linear power supplies (both repair and design), those trimpots are prime suspects. Especially those that are not Cermet.

[TERRA Operative]

Not working how?

It's a Disk eXPress V2.34 image and needs to be written back to static locations.
Also possibly including several CRC-32 checked parts so extracting manually can be time consuming.
The creating DXP software can also extract images.

The file DE000001.EXE should have at least /d and /t options.
(description and test)

Since static locations are needed maybe you should create a virtual disk as a destination.
DXP has also a disk interleave option, that's not optimal since it can be set to what ever.

It's a bit old stuff but some old Windows DOS box support may be available.

Once I unzip the file downloaded from the Dell website, I run the 'makedisk.bat' on my Dell Precision in DOS to create the boot floppy.
Then I boot to the floppy and I get the image below (Ignore the first two lines), where the computer hangs. (the 'CS4236B' device it finds is the onboard sound card)

I don't get any further than that.

I have a feeling it is a BIOS incompatibility with the last released version of the BIOS. I remember the utility did work once when I first got the PC, but after updating stuff, including the BIOS, it never worked again. If this is the case, I'm probably stuck unless I can find an old BIOS revision, which is probably going to be unobtanium...

I have found one ISA config utility disk image, but it don't work...

Try this, it did put up a fight and I switched virtual machines a lot but it looks promising.

I can extract these contents on the HDD of my Dell too, but it looks like the boot disk is supposed to unzip all this to a RAM Drive to run the application.

[TERRA Operative]

O. M. freaking Gee...


It was the GPU that was messing it all up! I removed the Quadro GPU and reinstalled the 3Dfx Voodoo3 3000 GPU and it now boots to the config utility!

Derp, I should have tried that ages ago.... Now, to do battle with the config utility and the jumpers on the card to get this National Instruments card working........

[m k]

You're still young.

Do you think it actually found what it says it found, a Cirrus Logic audio chip?

If the system can't handle all combinations you need to rearrange things more.
I remember that at least an SCSI of some sort and something else were mutually exclusive.
And if NI-card is short your situation is even more limited.

[TERRA Operative]

Ok, so I got the card somewhat configured, and the NI test utilities see the card now which is a good sign.

I tried running the Field Adjustment Software with things connected to my TDS784D Scope and it says nope no connection..
Not sure if it's FAS config or the cable. The FAS asks something about switch setting on install, which is as described:

The switch setting is the decimal translation of the binary number denoted by switches A9-A3 on a PCII card (A3 is LSB), or A13-A14 on a PCIIA card (A14 is LSB).
The switch pushed down on the OFF side represents a 1.
So for example, on a PCII card at its default, A9-A3 reads 101 0111 = 57hex = 87 decimal.

Which I'm pretty sure I have correct.

But it could be the cable too, as the GPIB card is right at the bottom slot in the PC case, so I can't get the cable plugged in 100%, so I think I'll need to source an extension adapter like a HP 10834A to extend the connection out a couple centimetres to let me attach the cable properly.
Anyone got an old adapter they don't need?


[EDIT] Nope, i thing the config still needs some love...

[Vince]

Got similar problem / frustration / anger / cursing moment when I tried to plug my GPIB cable my Tek 2232 scope 

So I need an extension too....

[Vince]

Yes, so many trimmers and the one time I really need one... I can't find the correct one ! 

I think I need to do some more component sorting and inventorying... need to inventory all these trimmers so I know what I need to buy to fill the gaps.

And some 10K 1/4W resistors as well...

With hindsight, I'm not surprised. As I tinkered a lot with linear power supplies (both repair and design), those trimpots are prime suspects. Especially those that are not Cermet.

What baffles me is that the failure mode here is that if the wiper contact goes bad /open circuit, or the track goes open circuit like it did here... it send the max/unregulated juice straight to the amp !
Why not engineer it to fail in safe way, and instead make the supply cut power ? 

I also don't get why they regulated the ground line rather than the positive line like everybody else on the planet.... is it just because QUAD is English so they like to drive ont he wrong side of the road ? IT's just them giving the middle finger to the rest of the world ? Makes my brain hurt when I look at the schematic...

Or is there an actually reason /. technical benefit in putting the pass transistor in the ground side rather V+ ?!
Maybe an advantage specific to audio amp applications ?!

Have been sick all day, so no lab activities for me this evening, hoping to be back on my feet and kicking tomorrow morning....

[Robert763]

One reason for putting the pass transistor in the negative rail is that the regulator circuit runs close to negative so does not need a "overhead" voltage to operate and is running at a lower voltage overall. If the transistor is in the positive rail the regulator needs to have a supply voltage above the output voltage so it can turn the output device on. This means the more power dissipation etc etc.
The regulated supply is one of the things that set the Quad amplifiers apart from others. It does improve the performance overall.

Robert.

[srb1954]

I also don't get why they regulated the ground line rather than the positive line like everybody else on the planet.... is it just because QUAD is English so they like to drive ont he wrong side of the road ? IT's just them giving the middle finger to the rest of the world ? Makes my brain hurt when I look at the schematic...

Or is there an actually reason /. technical benefit in putting the pass transistor in the ground side rather V+ ?!
Maybe an advantage specific to audio amp applications ?!

It is not just a Quad or English thing.

You occasionally see this configuration in older HP and Tektronix designs. It can result in simpler regulator circuits and back in the day, when every transistor cost real money, the design engineers were always looking for ways to save money on products by implementing the simplest possible circuits that achieved the specification requirements.

It certainly does make your brain hurt to analyse these circuits but you have to admire the skill of the engineers who came up with these circuits. Back then they had to synthesise and analyse these circuits with only pencil, paper and slide rule in their arsenal of design tools. We are totally spoilt these days with high powered computer systems, PCB layout S/W and circuit simulation S/W.

[Specmaster]

What baffles me is that the failure mode here is that if the wiper contact goes bad /open circuit, or the track goes open circuit like it did here... it send the max/unregulated juice straight to the amp !
Why not engineer it to fail in safe way, and instead make the supply cut power ? 

I also don't get why they regulated the ground line rather than the positive line like everybody else on the planet.... is it just because QUAD is English so they like to drive ont he wrong side of the road ? IT's just them giving the middle finger to the rest of the world ? Makes my brain hurt when I look at the schematic...

Or is there an actually reason /. technical benefit in putting the pass transistor in the ground side rather V+ ?!
Maybe an advantage specific to audio amp applications ?!

Have been sick all day, so no lab activities for me this evening, hoping to be back on my feet and kicking tomorrow morning....

Well not forgetting that you're dealing with a well renowned and respected Hi-Fi amplifier here, so it might also, on top of the other reasons you have been given, that it might help to reduce the overall noise level?

I hope you feel better  soon.

[vk6zgo]

I also don't get why they regulated the ground line rather than the positive line like everybody else on the planet.... is it just because QUAD is English so they like to drive ont he wrong side of the road ? IT's just them giving the middle finger to the rest of the world ? Makes my brain hurt when I look at the schematic...

Or is there an actually reason /. technical benefit in putting the pass transistor in the ground side rather V+ ?!
Maybe an advantage specific to audio amp applications ?!

It is not just a Quad or English thing.

You occasionally see this configuration in older HP and Tektronix designs. It can result in simpler regulator circuits and back in the day, when every transistor cost real money, the design engineers were always looking for ways to save money on products by implementing the simplest possible circuits that achieved the specification requirements.

It certainly does make your brain hurt to analyse these circuits but you have to admire the skill of the engineers who came up with these circuits. Back then they had to synthesise and analyse these circuits with only pencil, paper and slide rule in their arsenal of design tools. We are totally spoilt these days with high powered computer systems, PCB layout S/W and circuit simulation S/W.

It was also a quite common design in the early days of solid state regulation of high voltage supplies for tube circuitry.
Solid state had obvious advantages overusing tubes in regulators, but early transistors couldn't directly operate at 200-300 volts.
Although the Quad design is a later one, it does deal with quite high voltages.

[TERRA Operative]

WINNER WINNER CHICKEN DINNER!!

I got the freaking GPIB card working and the Field Adjustment Software talking to my TDS784D scope! 
Turns out besides the config needing tweaking, one of my NI GPIP-PCII/PCIIA cards is faulty... Good thing I had the hording tendancy foresight to buy two....


Holy shiet, it actually works! Time to get my levelled sinewave generators polished up and get ready for some hot and heavy calibration and adjustment action.


Also, I'll have to get a cheap proper LCD monitor too, the tiny 7" LCD I'm using now is a little too small to squint at for a long time.

[Vince]

Thanks for the replies on the pass transistor chaps ! 

Terra that's super cool, with your experience maybe I will too be able to get it working ! Because when I tried a few years ago, it could not connect or something, like you.
I too have two of these ISA NI cards !

I hope you will make a YT video on your channel about using that FAS / calibratiing the TDS, and post a link here.

I bet it's already being recorded as we speak !

Just woke up, still feel like crap but maybe I can feel it's improving, too soon to tell.
Left ear somehow feels strange, and not much signal coming from it... I am half deaf ! Hopefully it will clear up soon... hearing is an important sense when troubleshooting old electronics... can give you earliy warning of a catastrophe about to happen and the DUT explodes in your face....

[Vince]

QUAD 303 AUDIO AMP REPAIR

OK I am starting to feel better now... not quite well enough to feel safe working on dangerous stuff like my hollow state Tek scopes for example, but well enough to work on lower risk stuff like this low voltage little audio amp. Still deaf from the left ear though, hopefully that will clear up soon 

So I think I have figured it out.  Been busy buzzing every component on this driver board, pulling some of them to be 100% sure of the reading.

There is A LOT of damage on this board !!!   

If you look at the schematic, basically the left half of it is the low power stuff, and it's good. However the right half of the schematic, where the juice is... experience a catastrophic failure ! I noted in red all the failed components.

Remember taht the two shorted / failed TO3 driver transistors I had replaced earlier, were the ones driven by this board, so there was already that !
Then on the board itself

- The two medium power trannies that drove the T03, are bad too : Tr105 and Tr106

- x3 10R resistors were bad. One that was almost open circuit, and two others that looked a bit overheated, were reading too high, 13.5R, that's +35% ....

- A track on the PCB that vaporized, I had already noticed that a while back and soldered a jumper wire.


Then there is a section of the circuit half way vertically to the left of that area... it's Tr107. I think it dos the quiescent current adjustment thing, helped with a trimmer.  Well that transistor, a BC109C is dead. I immediately checked the trimmer that goes with it... yes it was open circuit like the one on the voltage regulation board ! 

So I guess the root cause of the problem was this trimmer failing, which killed the little transistor near, which caused big trouble with the quiescent current and it cascaded into ruining the 4 power trannies downstream ?

Anyway, as far as repairing all that mess :

1) The x3 10R resistors, got lucky, I have some AND they are not 1/4W but actually much bigger, same package size as the old ones !  So I have already fixed these.

2) Trimmer : 2.2K horizontal.... THAT ONE I do have in stock, too of them even !  So that's fixed as well.

3) The BC109C for the quiescent current. I have in stock load of BC107C which according to the datasheet is the same transistor, just slightly different specs. Higher voltage and different noise figure, 10dB instead of 4dB for the 109. Not sure how these noise thing works, s 10dB worse or better than 4dB ?! Should be good enough for troubleshooting purposes anyway, so that's fine. I can always put a new 109C later, they are still made apparently.

4) Remaining and by far biggest problem is replacing Tr105 / 106 !
They are RCA 38495 / 38496 but as usual with these silly RCA part number, no datasheet to be found anywhere ! I hate these old RCA parts !
However google is full of reference to these trannies !..... but only full of people who like me are trying to replace them on this very amp ! 

Found this website about this very QUAD 303 amp, that gives replacements :
http://quadrevisionspot.blogspot.com/2007/03/quad-303-replacement-transistors.html

Says he replaces these transistors with BC461 or 2N5322 ...but I checked and both come in mundane TO-39 packages, no the "mini TO3 " (don't know how it's called) that the old RCA came in ! Which means I can"t reused the existing heat sink !
I do have a few heat sinks that can mound on T039 cans, but they look very different ! So when looking at my pictures, the prospective buyer would instantanlty see that my replacement heat sinks do not match at all the original heat sinks on the other driver board a few inches away  !

Or... I replace the heat sink on the other board as well, to make it all look the same ?! 

However there is still a problem... the original heat sink is bigger than the small H/S I have for T039 packages, so the latter would run hotter than the former.

Also.... these " mini T03 " packages actually look like a regular TO39 packages, just with a thick oval plate welded onto them. So from a purely mechanical point of view.. I COULD fit a replacement T039 transistor into the old H/S... BUT of course it would only be good for show, and be zero for cooling since there would be zero heat transfer between the T039 can and the H/S, so the TO39 would overheat and die ! 

So.... no, I just don't see any satisfactory solution here.

I could maybe search for used original RCA transistors, but they would probably be sold for quite some money and more annoyingly you have no clue about their health.


So what do I do now  ?

For now, the aim is only to fix it and get it working electrically, not about being perfect in every respect.
So for now I have replaced the failed 109C with a 107C, and the old RCA I will replace with TIP 31/32 because I have that them in stock brand new, a few of them, enough voltage and current handling capability, and with their TO220 package they have enough metal to not melt, and of course I would not turn the amp full blast... just a low to moderate volume levels.

[Vince]

Hmmmm.... I am thinking of a potential solution to that mini-TO3 heatsink problem.

Maybe I could take the old trannies, and drill the can out of it, to salvage the oval metal plate part, then fit the replacement TO39 transistor in the plate, with a slightly loose fit, and use thermal "glue"  when fitting it, hoping the thermal bond would be sufficiently good ?!

[tautech]

Hmmmm.... I am thinking of a potential solution to that mini-TO3 heatsink problem.

Maybe I could take the old trannies, and drill the can out of it, to salvage the oval metal plate part, then fit the replacement TO39 transistor in the plate, with a slightly loose fit, and use thermal "glue"  when fitting it, hoping the thermal bond would be sufficiently good ?!

Instead replace the HS screws with longer ones and use the additional length to fasten a clamping bar atop any replacement trannie to clamp it to the HS.
Not pretty but perfectly functional.

[Specmaster]

QUAD 303 AUDIO AMP REPAIR

OK I am starting to feel better now... not quite well enough to feel safe working on dangerous stuff like my hollow state Tek scopes for example, but well enough to work on lower risk stuff like this low voltage little audio amp. Still deaf from the left ear though, hopefully that will clear up soon 

So I think I have figured it out.  Been busy buzzing every component on this driver board, pulling some of them to be 100% sure of the reading.

There is A LOT of damage on this board !!!   

If you look at the schematic, basically the left half of it is the low power stuff, and it's good. However the right half of the schematic, where the juice is... experience a catastrophic failure ! I noted in red all the failed components.

Remember taht the two shorted / failed TO3 driver transistors I had replaced earlier, were the ones driven by this board, so there was already that !
Then on the board itself

- The two medium power trannies that drove the T03, are bad too : Tr105 and Tr106

- x3 10R resistors were bad. One that was almost open circuit, and two others that looked a bit overheated, were reading too high, 13.5R, that's +35% ....

- A track on the PCB that vaporized, I had already noticed that a while back and soldered a jumper wire.


Then there is a section of the circuit half way vertically to the left of that area... it's Tr107. I think it dos the quiescent current adjustment thing, helped with a trimmer.  Well that transistor, a BC109C is dead. I immediately checked the trimmer that goes with it... yes it was open circuit like the one on the voltage regulation board ! 

So I guess the root cause of the problem was this trimmer failing, which killed the little transistor near, which caused big trouble with the quiescent current and it cascaded into ruining the 4 power trannies downstream ?

Anyway, as far as repairing all that mess :

1) The x3 10R resistors, got lucky, I have some AND they are not 1/4W but actually much bigger, same package size as the old ones !  So I have already fixed these.

2) Trimmer : 2.2K horizontal.... THAT ONE I do have in stock, too of them even !  So that's fixed as well.

3) The BC109C for the quiescent current. I have in stock load of BC107C which according to the datasheet is the same transistor, just slightly different specs. Higher voltage and different noise figure, 10dB instead of 4dB for the 109. Not sure how these noise thing works, s 10dB worse or better than 4dB ?! Should be good enough for troubleshooting purposes anyway, so that's fine. I can always put a new 109C later, they are still made apparently.

4) Remaining and by far biggest problem is replacing Tr105 / 106 !
They are RCA 38495 / 38496 but as usual with these silly RCA part number, no datasheet to be found anywhere ! I hate these old RCA parts !
However google is full of reference to these trannies !..... but only full of people who like me are trying to replace them on this very amp ! 

Found this website about this very QUAD 303 amp, that gives replacements :
[url]http://quadrevisionspot.blogspot.com/2007/03/quad-303-replacement-transistors.html[/url]

Says he replaces these transistors with BC461 or 2N5322 ...but I checked and both come in mundane TO-39 packages, no the "mini TO3 " (don't know how it's called) that the old RCA came in ! Which means I can"t reused the existing heat sink !
I do have a few heat sinks that can mound on T039 cans, but they look very different ! So when looking at my pictures, the prospective buyer would instantanlty see that my replacement heat sinks do not match at all the original heat sinks on the other driver board a few inches away  !

Or... I replace the heat sink on the other board as well, to make it all look the same ?! 

However there is still a problem... the original heat sink is bigger than the small H/S I have for T039 packages, so the latter would run hotter than the former.

Also.... these " mini T03 " packages actually look like a regular TO39 packages, just with a thick oval plate welded onto them. So from a purely mechanical point of view.. I COULD fit a replacement T039 transistor into the old H/S... BUT of course it would only be good for show, and be zero for cooling since there would be zero heat transfer between the T039 can and the H/S, so the TO39 would overheat and die ! 

So.... no, I just don't see any satisfactory solution here.

I could maybe search for used original RCA transistors, but they would probably be sold for quite some money and more annoyingly you have no clue about their health.


So what do I do now  ?

For now, the aim is only to fix it and get it working electrically, not about being perfect in every respect.
So for now I have replaced the failed 109C with a 107C, and the old RCA I will replace with TIP 31/32 because I have that them in stock brand new, a few of them, enough voltage and current handling capability, and with their TO220 package they have enough metal to not melt, and of course I would not turn the amp full blast... just a low to moderate volume levels.

This might help you, Vince.

TR1L/R: 38494 / 2N3055
TR2L/R: 38494 / 2N3055
TR3: 16012 / 40411 / MJ802
TR201: 38495 / 40409 / BC441
TR200: U17229 / BC556B
TR100: BC214C
TR101/TR107: BC109B / BC184B
TR102/TR103: ZTX304 / BC546B
TR104: ZTX504 / BC556B
TR105: 38496 / 2N5322 / BC461
TR106: 38495 / 2N5320 / BC441

This info was obtained by using google phoo and came from this site https://www.audioasylum.com/cgi/t.mpl?f=amp&m=24194

Another useful site is here https://www.diyaudio.com/community/threads/quad-303-replacement-components.344605/

https://www.dadaelectronics.eu/uploads/downloads/01_Dada-Electronics-Revision-Upgrade-Manuals/Quad-303-Converting-the-output-stage-to-NPN-PNP-V2.1.pdf

https://www.dadaelectronics.eu/uploads/downloads/01_Dada-Electronics-Revision-Upgrade-Manuals/Quad_303_DIY_illustrated_upgrade_guidelines_V2.0.pdf

https://www.dadaelectronics.eu/uploads/downloads/02_Quad-Service-Manuals/Quad-303-Illustrated-Service-Supplement.pdf

https://www.dadaelectronics.eu/uploads/downloads/02_Quad-Service-Manuals/Quad-303-Service-Manual.pdf

https://www.dadaelectronics.eu/uploads/downloads/03_Quad-User-Manuals/Quad-303-Instruction-book.pdf

There are loads of useful bit on the Dada site, just scroll down the list and I'd be surprised if you cannot find all the info you need.

[Vince]

Thanks Spec ! it confirms what I had posted before from another site 

i.e. looks like there is no modern replacement available in the original  "mini TO3 " package.

ANYWAY :  I replaced these two trannystors with TIP 31C/32C as mentionned ealier, connected one single 8 ohm speaker to one of the outputs and....

NO SMOKE ! No sparks either, no short, no circuit breaker tripping... that's a good start.

Then I made the lab quiet / turned the music off, and listened.... with no input signal applied ot the amp, I can't hear any "hum" out of the speaker, yeah !!!
I like that a lot, I hate hum.

So I guess my 4 new expensive snap-in caps are doing their job eh ?! 

Then I applied a singla using my sig gen.

The lowest amplitude it will do, 50mVpp, sine wave, 1kHz..... works fine ! I can hear the tone loud and clear, crisp.... even at only 50mVpp it's quite loud to my ear, I mean that singular of course since the left one still gives me no signal 

Then I switched the speaker to the other output... the other output works just fine as well 

Then I switched the speaker back and forth from one output to the other, so I can compare loudness.... they sound equally loud, both outputs are putting out a similar amount of juice.

So that's looking good !

Those TO220 TIP 31/32 are working just fine !

OK so now need to wire it tot eh 33 pre-amp and send some actuai music in the system, see if there is anything blatantly wrong / off with the sound.

But so far looks like I got it working and am now therefore in the finishing stages of the repairr : making things pretty and tidy so as not to scarce the future potential buyers ! 

[Vince]

EDIT to your edit spec : ye sI know Dada, Neper showed it to me. The site does not help at all with my problem.
All they do is sell the T039 transistors of the part numbers already mentioned everywhere else, but they have no replacement trannies in the original mini-TO3 package.

They could potentially solve my missing knob problem for the pre-amp, but alas the one I did is out of stock, tough luck...

[Zoli]

Thanks Spec ! it confirms what I had posted before from another site 

i.e. looks like there is no modern replacement available in the original  "mini TO3 " package.

ANYWAY :  I replaced these two trannystors with TIP 31C/32C as mentionned ealier, connected one single 8 ohm speaker to one of the outputs and....

NO SMOKE ! No sparks either, no short, no circuit breaker tripping... that's a good start.

Then I made the lab quiet / turned the music off, and listened.... with no input signal applied ot the amp, I can't hear any "hum" out of the speaker, yeah !!!
I like that a lot, I hate hum.

So I guess my 4 new expensive snap-in caps are doing their job eh ?! 

Then I applied a singla using my sig gen.

The lowest amplitude it will do, 50mVpp, sine wave, 1kHz..... works fine ! I can hear the tone loud and clear, crisp.... even at only 50mVpp it's quite loud to my ear, I mean that singular of course since the left one still gives me no signal 

Then I switched the speaker to the other output... the other output works just fine as well 

Then I switched the speaker back and forth from one output to the other, so I can compare loudness.... they sound equally loud, both outputs are putting out a similar amount of juice.

So that's looking good !

Those TO220 TIP 31/32 are working just fine !

OK so now need to wire it tot eh 33 pre-amp and send some actuai music in the system, see if there is anything blatantly wrong / off with the sound.

But so far looks like I got it working and am now therefore in the finishing stages of the repairr : making things pretty and tidy so as not to scarce the future potential buyers ! 

Connect the scope to the output, and check with some 1kHz square wave for bad behaviour(ringing, oscillations).

[Robert763]

The odd package has  name  TO205MA or MD.
You could remove the TO5 header from the flange and solder a standard TO5/39 package to it. Low temperature solder might be a good idea though.

[TERRA Operative]

Thanks Spec ! it confirms what I had posted before from another site 

i.e. looks like there is no modern replacement available in the original  "mini TO3 " package.

ANYWAY :  I replaced these two trannystors with TIP 31C/32C as mentionned ealier, connected one single 8 ohm speaker to one of the outputs and....

NO SMOKE ! No sparks either, no short, no circuit breaker tripping... that's a good start.

Then I made the lab quiet / turned the music off, and listened.... with no input signal applied ot the amp, I can't hear any "hum" out of the speaker, yeah !!!
I like that a lot, I hate hum.

So I guess my 4 new expensive snap-in caps are doing their job eh ?! 

Then I applied a singla using my sig gen.

The lowest amplitude it will do, 50mVpp, sine wave, 1kHz..... works fine ! I can hear the tone loud and clear, crisp.... even at only 50mVpp it's quite loud to my ear, I mean that singular of course since the left one still gives me no signal 

Then I switched the speaker to the other output... the other output works just fine as well 

Then I switched the speaker back and forth from one output to the other, so I can compare loudness.... they sound equally loud, both outputs are putting out a similar amount of juice.

So that's looking good !

Those TO220 TIP 31/32 are working just fine !

OK so now need to wire it tot eh 33 pre-amp and send some actuai music in the system, see if there is anything blatantly wrong / off with the sound.

But so far looks like I got it working and am now therefore in the finishing stages of the repairr : making things pretty and tidy so as not to scarce the future potential buyers ! 

Connect the scope to the output, and check with some 1kHz square wave for bad behaviour(ringing, oscillations).

And a dual-trace scope will let you visually compare both channels at the same time. Got some beefy 8ohm resistors to use as loads?

[Vince]

Connect the scope to the output, and check with some 1kHz square wave for bad behaviour(ringing, oscillations).

See below. Scopes directly at the speaker output at the back of the amp.
Looks really clean in the flesh (sorry for the crappy picture), certainly no oscillation.
However while probing on the driver board, atte wire that goes to the speaker coupling cap, I made some spark and now the sound is very faint... need to fix that now !
BTW that was on the GOOD board, not the one I am reconstructing, so double-bummer... 

Oh you just can't imagine how fed up I am with this thing and how impatient I am to see it go out the door...

The odd package has  name  TO205MA or MD.
You could remove the TO5 header from the flange and solder a standard TO5/39 package to it. Low temperature solder might be a good idea though.

Thanks ! 

As I said earlier I did consider reusing the flange but though of thermal glue to bond the replacement TO39 to the old flange.... did not think of soldering it !
My 50Watt weller just is not up to the job I fear. However now I think of it, I could just preheat the flange by other means ? On the gas cooker in the kitchen, or with the hot air rework station set to 350°C ?
Yeah....

As for low melting temp solder, I have my silver solder to work on the ceramic strips in my old Tek scopes. Think I have an inch or two this "chip quick" (or whatever it's called...) ultra low temp metal mixture, that's not actual solder though, but in this particular case I guess it's just fine since we want to conduct only heat, and not worried about conducting electrical signals....

Hmm yeah I like that ! Let's do that ! 

And a dual-trace scope will let you visually compare both channels at the same time. Got some beefy 8ohm resistors to use as loads?

No beefy loads but who needs that when I have actual speakers connected already ?!