Commodore 1084s-P1 CRT repair

[djos]

So I finally stopped procrastinating and started work on my Commodore 1084s-P1 CRT repair project. It should be fairly straight forward as the number 1 failure with these is the HOT going bang and taking the FlyBack transformer with it.

Required parts:






and this is as far as I got today before fatherly duties intervened:


At least it's fully discharged and im ready to start desoldering al the relevant components. 

[djos]

Finished off the HOT & FlyBack Transformer replacement today - just need to replace the power switch now as it doesnt stay on.

Components gone:


New ones in:


putting the neck board back together:


half done - J1 wire hasn't been soldered in yet:


and mostly back together:


and she works!


Some adjustments will be required (pic is too bright) but i'll sort that after I replace the power switch in a few days (it's in transit).

[SeanB]

Check all high value resistors ( anything over 10k) in the high voltage side, they do tend to drift high, and this causes the excessive brightness. Also resolder R3514, to make sure any hidden dry joint there does not kill the new parts.

[djos]

Check all high value resistors ( anything over 10k) in the high voltage side, they do tend to drift high, and this causes the excessive brightness. Also resolder R3514, to make sure any hidden dry joint there does not kill the new parts.

I haven't adjusted the "screen" pot on the Flyback yet, out of the box it's usually set too high.

Thanks for the tip, I'll definitely check the resistors and the solder on R3514. Can you reliably measure resistance in circuit?

[vk6zgo]

 
You are fixing a Monitor.
The big glass thing is the CRT

Calling the whole thing a "CRT" is an incredibly annoying species of "Computer person speak" which has no place in an electronics forum.

[djos]

You are fixing a Monitor.
The big glass thing is the CRT

Calling the whole thing a "CRT" is an incredibly annoying species of "Computer person speak" which has no place in an electronics forum.

Lol, it's still using cathode ray tube technology, it's just a very highly developed distant cousin.

[djos]

Ok, I turned the "screen" pot down on the FBT and it's no longer over driving the screen. 

I just need to hook up a video source and finish tweaking.

[djos]

and now focused.



I checked all the solder joints with my 5x illuminated glass and they all look fine - I couldnt even find R3514 on mine so it might be only on other models? (mine is the -P1)

Mine's obviously been repaired once before as there are quite a few solder joints with non factory rosin around them that wasn't cleaned off with IPA.

[vk6zgo]

You are fixing a Monitor.
The big glass thing is the CRT

Calling the whole thing a "CRT" is an incredibly annoying species of "Computer person speak" which has no place in an electronics forum.

Lol, it's still using cathode ray tube technology, it's just a very highly developed distant cousin.

My rant was a bit "tongue in cheek", but it does annoy me.
The CRT is just one component of the equipment you are fixing, & the only component which utilises "cathode rays".
All the other active devices are semiconductor based.

Some people used to refer to cars as "motors", or transistor radios as "transistors".(& probably still do)
It sounded silly then, & it does now when the same thing is done with Monitors.

It can also be misleading to beginners.
On another thread someone was getting all overwrought about the dangers of CRT tubes because they read on a "computer" website that there was some large amount of lead inside the "CRT".

The website was, of course, referring to the whole Monitor, & including the amount of lead in the PCB & other soldered connections.

[Bruce Abbott]

Calling the whole thing a "CRT" is an incredibly annoying species of "Computer person speak" which has no place in an electronics forum.

CRT is short for 'CRT monitor' which is the whole thing. If you think acronyms have no place in an electronics forum then you can expect to continue being incredibly annoyed.
 

[Gyro]

CRT is short for 'CRT monitor' which is the whole thing. If you think acronyms have no place in an electronics forum then you can expect to continue being incredibly annoyed.

Err, CRT is short for Cathode Ray Tube, nothing more. It's a standalone component.  It could be in a TV, a scope, spectum analyser, camera... or a monitor

It can also be misleading to beginners.
On another thread someone was getting all overwrought about the dangers of CRT tubes because they read on a "computer" website that there was some large amount of lead inside the "CRT".

The website was, of course, referring to the whole Monitor, & including the amount of lead in the PCB & other soldered connections.

CRTs in TVs and Colour monitors use leaded glass in the faceplates to minimise X-ray emission. You should be very careful not to store Port or Sherry  in them for long periods (as is the advice for Lead glass decanters) for fear of Lead leaching. 

P.S. "CRT tube" is a tautology. 

[djos]

It's a silly argument, although I do get irritated by OEM's calling LCD tv's led tv's when only the backlight is led and the display itself uses an LCD panel. 

[Gyro]

Me too - they'd have been really screwed it they hadn't used Organic LEDs in OLED TVs.

P.S. Yes, I agree - Just Saturday evening high spirits in my case. Don't worry, it's worn off now.

P.P.S. We all know we should be talking about VDUs anyway.

[vk6zgo]

CRT is short for 'CRT monitor' which is the whole thing. If you think acronyms have no place in an electronics forum then you can expect to continue being incredibly annoyed.

Err, CRT is short for Cathode Ray Tube, nothing more. It's a standalone component.  It could be in a TV, a scope, spectum analyser, camera... or a monitor

It can also be misleading to beginners.
On another thread someone was getting all overwrought about the dangers of CRT tubes because they read on a "computer" website that there was some large amount of lead inside the "CRT".

The website was, of course, referring to the whole Monitor, & including the amount of lead in the PCB & other soldered connections.

CRTs in TVs and Colour monitors use leaded glass in the faceplates to minimise X-ray emission. You should be very careful not to store Port or Sherry  in them for long periods (as is the advice for Lead glass decanters) for fear of Lead leaching. 

Yes, but Cathode Ray Tubes are unlikely to have Port or Sherry stored in them.
I don't usually store Port for very long at all! 

He actually linked to the website, & from context, & the mass quoted, it was definitely to do with the amount of solder in the monitor.

P.S. "CRT tube" is a tautology. 

You got me there!
I noticed I had done that, & considered doing battle with the iPad to edit it, then decided "To hell with it, let someone have some harmless fun!"

[Bruce Abbott]

I do get irritated by OEM's calling LCD tv's led tv's when only the backlight is led and the display itself uses an LCD panel. 

Definition of: LED TV

A flat panel LCD TV set that uses LEDs (light emitting diodes) for its backlight source rather than the earlier cold cathode fluorescent lamps (see CCFL). Smaller, more power efficient and having a greater optical range than the fluorescents, LED TVs produce deeper blacks and more saturated color. In 2005, Sony offered the first LED TV.

Although an LED TV is really an LCD TV with LED backlighting, the industry branded them as LED TVs to avoid monikers such as "LED backlit TV" or "LED-based LCD TV.".

[djos]

I do get irritated by OEM's calling LCD tv's led tv's when only the backlight is led and the display itself uses an LCD panel. 

Definition of: LED TV

A flat panel LCD TV set that uses LEDs (light emitting diodes) for its backlight source rather than the earlier cold cathode fluorescent lamps (see CCFL). Smaller, more power efficient and having a greater optical range than the fluorescents, LED TVs produce deeper blacks and more saturated color. In 2005, Sony offered the first LED TV.

Although an LED TV is really an LCD TV with LED backlighting, the industry branded them as LED TVs to avoid monikers such as "LED backlit TV" or "LED-based LCD TV.".

I'm well aware of why, still doesnt change the fact that "LED TV's" are nothing of the sort, they are LCD TV's with an LED backlight - we didnt stop calling them LCD Screens when front lighting was first used, or when backlighting replaced front lighting.

So in summary, "LED TV" =  marketing BS.

At least Plasma and OLED screens are accurately named.

[djos]

Replacement power switch finally arrived today after the courier company lost it and mysteriously delivered it to my mailbox 4 days after claiming to have delivered it too me in person (including me signing for it apparently). Amazing how responsive they can be when you accuse their driver of fraud! 



Unfortunately I'm of crook atm, so can't install it for a few days.

[BubbaMc]

Nice work.

Is that the model with a live chassis?

BTW feed it an RGB picture if you want to see how good it is

[djos]

Nice work.

Is that the model with a live chassis?

BTW feed it an RGB picture if you want to see how good it is

Cheers.

Not sure what you mean by live chassis? The chassis is plastic so non-conductive.

Yeah I'll be testing and focusing it properly, with an Amiga putting out RGB, once I've recovered from a nasty bout of gastro that the daughter brought home from school.

[BubbaMc]

Not sure what you mean by live chassis?

See here for a brief discussion: https://www.eevblog.com/forum/beginners/live-chassis/

One of my later model 1084S monitors has a live chassis (assume Commodore did this as a cost saving measure), so I'm not willing to attempt repair until I get an isolation transformer.

[djos]

Not sure what you mean by live chassis?

See here for a brief discussion: https://www.eevblog.com/forum/beginners/live-chassis/

One of my later model 1084S monitors has a live chassis (assume Commodore did this as a cost saving measure), so I'm not willing to attempt repair until I get an isolation transformer.

Hmmm, I'd have to take a closer look at mine but seeing as it's a rebadged Philips Im not terribly concerned. The main danger with these is the FBT, if you dont discharge them properly before starting work on them you can end up with a paralysed arm and a nasty headache for a few hours. I recall being dismissive once back in the 90's while working on a 21" Trinitron, the jolt I got that day corrected that dismissiveness permanently and so now i'm paranoid instead!   

EDIT: there's grounding wires between all the boards and there's no live chassis that I can see - imo it's a pretty nice design.

[helius]

A lot of the reputation "live-chassis" sets have comes from the bad old days of vacuum tube rectifiers and unpolarized flex. TVs from that era did not have video in jacks because they would be unsafe, since the mains might be conducted onto the shield of the video cable!

Even if a computer monitor is not fully isolated, it can't literally be live on the chassis without conducting the mains into the computer equipment. While it may be good practice to use isolation transformers, it is not the same level of risk as the former designs.

[BubbaMc]

Good to know, thanks.

[djos]

So I'm finally recovered from a nasty dose of Gastro and made it back out to the workshop to finish off my 1084s repair:

Old switch gone:


new switch in:



Picture quality tweaked to perfection using my little a600 (finally found a use for it! Workshop Amiga!):


yeah baby:



Soooo, i was very happy .... until the new switch failed after half a dozen uses! 

Wagner Online are going to be getting a very sternly worded email from me shortly! 

[Alex Eisenhut]

I had no idea there was a 1084 with a bezel looking like the 1950. Thanks for sharing!