Author Topic: HV PSU resto, metal rectifiers  (Read 14333 times)

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Offline GK

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HV PSU resto, metal rectifiers
« on: February 27, 2015, 08:24:18 am »
I'm restoring three variable, electronically regulated HV power supplies: A Siemens/Ediswan Model R1103A and a pair of Marconi model TF1109A's. The units are almost identical, the Siemens/Ediswan version differing mostly in chassis layout, and has an updated circuit having a separate rectified and filtered screen supply for the series-pass tubes, whereas in the Marconi version the tubes (12E1's) are just connected as triodes. 

I'm ditching all of the original capacitors and the carbon resistors will be replaced as well. Most of the resistors measure quite a bit (higher) out of tolerance, as old carbon resistors a prone to do.

With the goal of long-term reliability, I was originally planning to ditch the metal/selenium rectifiers for modern silicon, but after checking them out on my Tek 575 curve tracer and finding them operationally fine, I've decided to keep them just for the original and "cool" factor. The main, unregulated HT rail is full-wave bridge rectified by a pair of these diode stacks. Each stack is has an electrical connection to the central plate/cooling fin, so they are essentially "wired" as two series connected diodes per stack. The central connections of a pair go to the transformer secondary. I've tested each diode connection of each stack individually and they all measure very consistently the same, dropping approximately 35V at a forward current of 200mA and having no reverse current of consequence.

The rectifiers need a good clean/paint strip and repaint after rust conversion. I was about to start by just dunking these in solvent, but I'm not so sure. I know that the selenium in these things is deposited on the stacked coins in a very thin layer but I have no idea just how fragile/susceptible these things are to mechanical handling and dipping in solvent. Does anyone out there have have any idea?


This metal rectifier was once a home for wasps:



On the curve tracer:





The Siemens / Ediswan incarnation:



The two Marconi units almost stripped:



Capacitors for the bin:

« Last Edit: February 27, 2015, 08:41:31 am by GK »
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Online T3sl4co1l

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Re: HV PSU resto, metal rectifiers
« Reply #1 on: February 27, 2015, 12:52:27 pm »
I bet those capacitors are full of healthy stuff... :o

Tim
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Offline amyk

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Re: HV PSU resto, metal rectifiers
« Reply #2 on: February 27, 2015, 01:50:19 pm »
The Nitrogol caps don't contain any PCBs, despite the scary-sounding name.

P.S. you might be able to sell them, it seems there's a market for audiophiles(fools?) buying "vintage" capacitors.
 

Offline JacquesBBB

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Re: HV PSU resto, metal rectifiers
« Reply #3 on: February 27, 2015, 02:18:30 pm »
Is it always necessary to ditch these high voltage capacitors ?

I have  two HV tube power supply that  are waiting in my workshop for some
time on my side to rejuvenate them.

One is a 300V power supply.
I already checked some of these capacitors (10uF, 550V electrolytic or  2.2uF 630 V paper), and they had (from memory)
relatively good properties :  cap value close to original, and  relatively low ESR.

The other one is a 3kV PSU (Fluke 415b)  with  2uF 3kV oil caps that are not that easy/cheap  to find.
Somewhat similar ones can be found
(277$ each (by 8 ) at Mouser) (see attached pict)
« Last Edit: February 27, 2015, 03:59:12 pm by JacquesBBB »
 

Online T3sl4co1l

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Re: HV PSU resto, metal rectifiers
« Reply #4 on: February 27, 2015, 04:12:20 pm »
The main problems are, if they are leaky (moisture ingress?) or leaky (oozing PCBs), they should be disposed of appropriately.

If they're actually PCB free, and not leaking, heck, they're probably fine, leave 'em in for another 50 years!

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Offline JacquesBBB

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Re: HV PSU resto, metal rectifiers
« Reply #5 on: February 27, 2015, 04:18:09 pm »
Not leaking,  but probably not PCB  free.
 

Offline SeanB

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Re: HV PSU resto, metal rectifiers
« Reply #6 on: February 27, 2015, 05:21:04 pm »
Do not dip those rectifiers in anything, just use a brush and get the dust off. Paint solvents will penetrate the existing paint ( likely a duco with the age of them) and will very quickly give out that magic incredibly bad smelling smell that you will instantly know is a dying selenium rectifier. the only protection is to use a small brush and grey paint on the fins, not getting anywhere near the middle if you want, but they work fine with a slight rust on the fins.

As to the HV blocks, as long as the glass seals are intact use them, if they start to leak or weep replace. They are very rare that they fail and generally last till the case rots through underneath. With the construction being basically oil soaked paper and thick foil the replacements will not last, as they are wound with thinner insulation and close to transparent foils.

If you do replace the stack rectifiers keep the originals in place and wire the replacement microwave oven diodes and series resistors up under the chassis, so it still looks original from the top.
 

Offline GK

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Re: HV PSU resto, metal rectifiers
« Reply #7 on: February 28, 2015, 12:28:58 am »
I have a boot full of these old paper capacitors from various pieces of equipment and I am disposing of all of them. I've had more than one leakage incident (from otherwise perfect looking caps) and I just don't want that crap and potential bother in my shack anymore. Whats worse is that these caps when chassis mounted are typically mounted facing down (as they are in the Marconi supplies) , so when the glass/ceramic seals finally give out you have oil of unknown composition dribbling down the inside of your equipment rack onto and through the instruments beneath.

The rectifiers look a lot better in the photos than they do in real life. The paint is flaking quite badly and on one the rust is particularly severe on the underside. They need at minimum a mechanical clean and a dip or brushing in rust converter before repaint. I'll avoid the use of solvent.
 
« Last Edit: March 01, 2015, 11:47:05 am by GK »
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Offline TSL

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Re: HV PSU resto, metal rectifiers
« Reply #8 on: February 28, 2015, 02:54:59 am »
I've see restorations where caps like those have been carefully disassembled, contents discarded, and a new cap placed inside the metal container so the build still has the same "look"

cheers

Tim
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Offline c4757p

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Re: HV PSU resto, metal rectifiers
« Reply #9 on: February 28, 2015, 03:05:31 am »
I've see restorations where caps like those have been carefully disassembled, contents discarded, and a new cap placed inside the metal container so the build still has the same "look"

I hate this so much.
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Offline GK

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Re: HV PSU resto, metal rectifiers
« Reply #10 on: February 28, 2015, 09:13:08 am »
I ended up cleaning the rectifiers in a methylated spirit bath. A wire brush with bristles long enough to reach down to the center was used to scrape away all of the paint that was flaking. Then another dip in the metho, a thorough blast with compressed air and then a dip in rust converter. A couple of hours later once the rust converter had done its job, turning the surface rust into a tough, paintable black oxide, the rectifiers were given a final going over with the wire bush, a final metho bath for a clean and then a spray of flat black engine enamel (what I had on the shelf).

Here is one of the rectifiers just after rust conversion:



Fresh after applying the final coat of paint:



The chassis' of these Marconi supplies are raw, non-anodized aluminum. You can polish such as chassis up and it'll look all nice and pretty immediately after, but in the long term it will always develop an unsightly oxide layer and especially so in an open chassis design such as this, in which dust inevitably harboring a degree of moisture from the air will settle on the chassis. So I painted them with an automotive engine enamel formulated for cast aluminum. Tomorrow I'll bake them in my oven at 90 deg. C for an hour each.



The front panel for one of these Marconi supplies had a pair of additional holes drilled for some kind of modification at some time in its life. The holes were filled with an epoxy putty by Selleys called "Knead It". One hardened it was sanded back flat with 240 grit sandpaper.





You often find some interesting things restoring old stuff, like this for instance. One of the big 1000V 8uF oil-filled caps was originally clamped down on top of one of the wiring looms. The insulation of the wires were actually cut right through to the copper, but the layer of paint on the capacitor housing must have been a sufficient insulator because the power supply was operational in this state for decades.




« Last Edit: March 01, 2015, 11:46:46 am by GK »
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Offline GK

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Re: HV PSU resto, metal rectifiers
« Reply #11 on: February 28, 2015, 09:32:07 am »
I've see restorations where caps like those have been carefully disassembled, contents discarded, and a new cap placed inside the metal container so the build still has the same "look"


I've done this myself in pieces of equipment of particular value, such as my WWII transceivers and transmitters, which are, essentially, functional museum pieces. Despite the drool it seems it incite in some it's a perfectly legitimate part of making operational a piece of kit that would otherwise be devalued if it was unduly modified from standard form.

As for these HV power supplies, I don't really care about originality as they have minimal value and unrepaired would be just destined for the tip. I'm mostly just interested in getting a trio of operational and useful HV power supplies going for my workbench. Though there is of course still the "coolness" factor of making reliable and pressing into service kit with pretty glowing valves.
« Last Edit: February 28, 2015, 09:39:17 am by GK »
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Offline GK

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Re: HV PSU resto, metal rectifiers
« Reply #12 on: February 28, 2015, 09:54:12 am »
The Nitrogol caps don't contain any PCBs, despite the scary-sounding name.


Hmm... The others are TCC brand "Visconol". Any idea about those?
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Offline GK

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Re: HV PSU resto, metal rectifiers
« Reply #13 on: February 28, 2015, 11:53:12 am »
Back on the curve tracer and all is hunky-dory.

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Re: HV PSU resto, metal rectifiers
« Reply #14 on: February 28, 2015, 02:50:02 pm »
Black selenium rectifiers, sexy 8)

If you wanted to preserve the shine-able chassis, anodize would leave a dull but robust finish; you'd need a clear coat to really keep it shiny.

Probably not really robust for something like this, and anyway, it's an ugly bit of rackmount kit, drab military-industrial colors are perfect. ;)

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Offline amyk

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Re: HV PSU resto, metal rectifiers
« Reply #15 on: February 28, 2015, 04:15:05 pm »
The Nitrogol caps don't contain any PCBs, despite the scary-sounding name.


Hmm... The others are TCC brand "Visconol". Any idea about those?
According to this:
http://www.scew.gov.au/sites/www.scew.gov.au/files/resources/378b7018-8f2a-8174-3928-2056b44bf9b0/files/anzecc-gl-identification-pcb-containing-capacitors-information-booklet-electricians-and-electrical.pdf

TCC Visconol shouldn't have PCBs, but TCC also produced caps with PCBs, so look at the model number.
 

Offline GK

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Re: HV PSU resto, metal rectifiers
« Reply #16 on: March 01, 2015, 11:38:06 am »
Probably not really robust for something like this, and anyway, it's an ugly bit of rackmount kit, drab military-industrial colors are perfect. ;)


I have an assortment of left over paints from a prior project.


« Last Edit: March 01, 2015, 11:46:21 am by GK »
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Offline GK

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Re: HV PSU resto, metal rectifiers
« Reply #17 on: March 01, 2015, 11:41:58 am »
Getting closer......

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Offline GK

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Re: HV PSU resto, metal rectifiers
« Reply #18 on: March 01, 2015, 11:51:10 am »
The Nitrogol caps don't contain any PCBs, despite the scary-sounding name.


Hmm... The others are TCC brand "Visconol". Any idea about those?
According to this:
http://www.scew.gov.au/sites/www.scew.gov.au/files/resources/378b7018-8f2a-8174-3928-2056b44bf9b0/files/anzecc-gl-identification-pcb-containing-capacitors-information-booklet-electricians-and-electrical.pdf

TCC Visconol shouldn't have PCBs, but TCC also produced caps with PCBs, so look at the model number.


lol, thanks for the reminder. I have that document somewhere (one of the gazillion pdf's stored on my hard disk) but had forgotten all about it.
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Online T3sl4co1l

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Re: HV PSU resto, metal rectifiers
« Reply #19 on: March 01, 2015, 04:36:45 pm »
Probably not really robust for something like this, and anyway, it's an ugly bit of rackmount kit, drab military-industrial colors are perfect. ;)


I have an assortment of left over paints from a prior project.

Well damn, I sure called that one :-DD

About as pretty as olive-drab can be :-+ :-+
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Offline SeanB

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Re: HV PSU resto, metal rectifiers
« Reply #20 on: March 01, 2015, 05:24:00 pm »
Olive drab never shined that good, I used to paint it in pretty patterns, mixing the olive drab, light earth and dark earth along with flat black as patterning. Then I moved, and it was all grey and sky blue. i did change the inner part colours I used though, from matt black to satin black, it was just as dark but looked ( and wore better) almost the same.
 

Offline tautech

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Re: HV PSU resto, metal rectifiers
« Reply #21 on: March 01, 2015, 07:10:45 pm »
Probably not really robust for something like this, and anyway, it's an ugly bit of rackmount kit, drab military-industrial colors are perfect. ;)

I have an assortment of left over paints from a prior project.

Series 2 landy if i'm not mistaken?

Chuck a 186 holden and Rover 90 Diff heads in it.  :-+

Your workshops tooooooo big.  :rant:
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Offline SeanB

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Re: HV PSU resto, metal rectifiers
« Reply #22 on: March 01, 2015, 08:38:36 pm »
Did you fix all the oil leaks, or did it all run out.
 

Offline GK

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Re: HV PSU resto, metal rectifiers
« Reply #23 on: March 02, 2015, 07:43:34 am »
SIIA 109" with Aust. Army-modified front guards.

I think the original 2.25L is a better motor than the Holden 6. I fully reconditioned mine and it is purring like a kitten. Though someone for who knows what reason molested mine by fitting a crappy Holden 6 Stromberg carburetor. I ditched that and rebuilt an original Solex (a much better unit) from several defunct donors.

Did you fix all the oil leaks,

Yes.

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Offline tautech

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Re: HV PSU resto, metal rectifiers
« Reply #24 on: March 02, 2015, 08:41:38 am »
SIIA 109" with Aust. Army-modified front guards.

I think the original 2.25L is a better motor than the Holden 6. I fully reconditioned mine and it is purring like a kitten. Though someone for who knows what reason molested mine by fitting a crappy Holden 6 Stromberg carburetor. I ditched that and rebuilt an original Solex (a much better unit) from several defunct donors.
I had a SIII with Rover 90 DH's, IIA box & TC with OD behind a Yellow Terror Hi-Torque Head 186 STD manifolds & carbie.
Reasonably happy @100 Km/h but at 90 would do mid to high 20's MPG.

The 2 1/4 L Rovers would run nice but nowhere near the torque or power of the 186.
And they only had a 3 bearing crank.  :palm:

Your's being ex-military would probably have dual tanks and the heavier springs?
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