Topcat's Dream Service Bench Reborn!

[Topcat]

Speaking of Sencore.....Split off from the cheap/free score thread, since this project is picking up steam & getting more involved....

This thread will serve as a log for a service bench I'm building for service work a little beyond simple recapping & PC work....even though this stuff is older legacy-style equipment, its still quite functional.



I won't say it's a 'cheap/free score', I bought this new (along with many other Sencore devices) back in the 90's when I had the service center. I still have them all, I didn't have the heart to sell them when I sold the business (they weren't included with the sale)....I didn't need the money, so they've been in boxes and lugged around with me ever since. They've been in the attic of my shop since I bought it in 2005. Until today, the LC102 and the PR570 were the only ones in use, and are used every day. THe sc3100 scope got brought out to work on a tricky PSU that came across my bench....and holy shit, I'm rusty!! I totally forgot how to use this thing! The other pieces are completely useless & obsolete, old school TV, VCR, and computer monitor analyzers.....but they would still make for a cool looking bench, but right now I just don't have the room on my service bench....so the rest stay in the attic....until I build another service bench (actually in the plans).

[stj]

Re: Topcat's Dream Service Bench Reborn!

nice,
what's the lcd display for?
btw, go find the power button before it gets stepped on or something!

[Topcat]

Re: Topcat's Dream Service Bench Reborn!

^
The power button has been lost for years.... The LCD shows voltages and other stuff (frequency counter). There's also a basic VOM feature, which shows in that display.

[TechGeek]

Re: Topcat's Dream Service Bench Reborn!

You have a computer monitor analyzer? That's cool! I guess that's for CRT monitors?

[Topcat]

Re: Topcat's Dream Service Bench Reborn!

You have a computer monitor analyzer? That's cool! I guess that's for CRT monitors?

Yes, it was intended for CRT's....but there's a resolution tester (tech programmable resolutions, refresh rates, etc) with a bar/pattern generator, which will work on anything with a 15-pin VGA connector.....so it could be used to dial in a LCD.

[TechGeek]

Re: Topcat's Dream Service Bench Reborn!

I could use one of them with those Gateway monitors... both of them probably need their geometry gone over extensively after a recap.

[Topcat]

Re: Topcat's Dream Service Bench Reborn!

Speaking of Sencore.....

Well, speaking of Sencore yet again....I've been back in the attic, and another long lost friend reappeared in the world....but first, a box came down containing a few random smaller things....

2x Topward dual output bench supplies (TPS-4000 and TPS-4000D) & Leader CRT rejuvenator.... These pieces were heavily used by me back in the day. I've fixed countless projection screen TV's with the rejuvenator. You shoot those CRT's up as if they were single-gun B&W....brought many back to life....and the bench supplies were useful for well....yea, do you really need me to tell you what a bench power supply is good for?!



...and some random vintage 50's/60's Sencore testers that came in lot from a shop I bought out nearly 25 years ago. I never used these, but I never got rid of them either.



...and another worthless but interesting piece of Sencore stuff, VC93 VCR tester:



This was another I bought new.....it wasn't heavily used, as 95% of VCR malfunctions back in my service center days were mechanical issues....such as belts, tires, dirty heads...... Very seldom did I have to use this, it wasn't one of my smarter purchases, but what did I know....I was young.

I still have all its accessories....


I have several more of these Sencore machines of this era to locate. I am planning on building another service bench for other things....and if nothing else, these will display well....with the exception of the variac, cap checker, and scope, the rest are pretty useless.....but I think I just wanted to see them all again. There's just something magical about old test equipment.

[Topcat]

Re: Topcat's Dream Service Bench Reborn!

I fixed the older dual output bench supply this morning, the TPS-4000. After 20 years of attic dwelling, the pots were all mucked up... Nothing a good cleaning wouldn't fix, and now the outputs are stable! I thought about recapping it, but I pulled a couple and they were all in spec....so I didn't bother... THis machine was old and used when I got it 25yrs ago.



Back in the day, this was heavily used for testing/servicing car audio equipment.....so 13.8v was always set on output 1. Output 2 was used for everything else.

[Topcat]

Re: Topcat's Dream Service Bench Reborn!

I cracked open the other one (the TPS-4000D), it's pots were gunked up too....and discovered a new brand of cap I've never heard of......so I may be recapping this one....some Teapo's from the 67's or 70's, I'm not really sure how old this thing is....

blown out and potentiometers cleaned.


Now for the new mystery cap: URANUS caps?!


Anothr big teapo & a beefy transformer.


Stable voltages now.


Cleaned up.


I didn't check any of these caps....as I think I'll find some replacements and redo it anyway.

[stj]

Re: Topcat's Dream Service Bench Reborn!

never mind the psu, lets see that nixi-tube multimeter!!
it looks like a bit of old hifi gear!!!!

[Topcat]

Re: Topcat's Dream Service Bench Reborn!

Funny you should ask about that....

[stj]

Re: Topcat's Dream Service Bench Reborn!

nice!

too bad about the zinc handles, but filing the stubs and some paint and it will look nice.

[Topcat]

Re: Topcat's Dream Service Bench Reborn!

nice!

too bad about the zinc handles, but filing the stubs and some paint and it will look nice.

Yea, the USPS played basketball with it I think. A friend of mine in Corpus Christi, TX bought a storage lot loaded with these and some really old modular HP & Tektronix oscilloscopes. He gave this meter to me, but the USPS pulverized it.

[Topcat]

Re: Topcat's Dream Service Bench Reborn!

I was tinkering with this and bumped it, channel 2 (slave) went dead....I bumped it again, it woke back up.... After an hour of poking around at it, I found a cracked solder joint on its regulator board.

I went ahead and recapped it while I was in there, all except the large filter cap (I didn't have any on-hand, it takes 2). I was checking them as I removed them and found several out of tolerance, but not alarmingly so....but for their age, a recap was warranted.

Purty Rubies, Slave board.


...and more Rubies, Master board.


Alive again!


Old caps.

[Topcat]

Re: Topcat's Dream Service Bench Reborn!

Honorable mention for an old relic...

[Topcat]

Re: Topcat's Dream Service Bench Reborn!

My old vectorscope made a reappearance in the world today. After ~18yrs stored away, it didn't work anymore.





After replacing a fuse and cleaning some pots, I got the beam back.....


After that, I had a feeling something else was wrong.....hmmmm....after pondering a few minutes, it hit me...dumbshit, its a vectorscope, and I realized that the backlight for the grid was not working.....the flashlight test.

Before:


After:


The culprit.....all 5 of these bulbs are bad.



There's +40v present @ the interface, the bulbs are just toast. Good opportunity to convert it to LED. I just have to create something to reduce the voltage and replace the bulbs with LED's. Yes, this is a pretty useless piece of equipment today, it was used back in the day for analog AV troubleshooting/tuning. I picked this up used from a debunked shop for peanuts, I think I used it maybe once or twice. It's a complete waste of time working on it.....but it needs to work again.

[TechGeek]

Re: Topcat's Dream Service Bench Reborn!

That might look to still be useful for tracing out color video circuits (e.g. when repairing an older TV)

[Topcat]

Re: Topcat's Dream Service Bench Reborn!

Ok, LED conversion complete. I went to a local place that's sells commercial-grade OSRAM stuff and asked what LED stuff they had.... The clerk (super nice guy) snipped a 6" section off a LED strip he had and said give this a whirl.....wouldn't accept any money, as long as I reported back with the results.... Fair enough.

These are 12v LED's....so first & foremost, test using a 12v bench supply....they lit.



I just laid them over where they will be to see what it would do.... Looks better than the original bulbs ever did.



Ok, then came the fun part.....I very well can't feed them 40v, which is present on the header.....so I began poking around the power supply, surely there has to be a +12v rail in here somewhere. The 3rd output I checked, sure enough, +11.98!! I'm hypothesizing these bulbs were originally rated @ 28v. Put 5 in parallel across that header, I'd guess the impedance would drop the 40v to ~28v....what lead me to that conclusion, when I initially searched for replacement bulbs, the highest rating I could find in that size was 28v, nothing higher.

So now comes board removal and rerouting.


I cut the trace feeding the +40v pin after verifying that the negative side was indeed ground. Then a simple jumper from a +12v regulator output to the backlight Vcc position.



Now to prepare the LED strip...
Here's what I was given:


Trimmed down to the size of the PCB.


adhesive strip attached directly to the PCB.


As if by some miracle, the solder holes on the strip lined up perfect with the through holes on the bulb PCB.


Powerup & test:


YAY, works!


Reassembled, tested again:


...and off...


That was today's positive accomplishment! The original lights gave off an yellow/orange-ish light, which I always thought made the grid look awful. These are obviously white LED's, which make the display look much nicer.....which is kind of sad, since this thing will probably never be used for its intended purpose.....but maybe I'll get to troubleshoot some old TV & other A/V equipment some day....until then, it sure makes a neat conversation piece....and I wanted to see it work again.

[Topcat]

Re: Topcat's Dream Service Bench Reborn!

Ok, I got around to testing my VG91 & TV92. The TV92 won't work without the VG91. The TV92 was an option when you buy the VG91. I fired the VG91 up, and the first thing I discovered was the LCD backlight was out....it's a standard segmented LCD though, perfectly legible without being lit...but I did repair the backlight, I'll get back to that momentarily. When I connected it to a TV, I also noticed the RF out was snowy & weak (whens the last time that was ever an issue), and the composite out was non-working.....so time to crack it open....

Apart!




Lo & behold!! A bad Panasonic cap!


I wont go into a big thing over the backlight. It was basically a LED conversion similar to the vectorscope. The original backlight was some kind of weird 'indiglo' setup that was ever-so popular in the 90s. I just did a LED conversion off a +12v rail and called it a day.



Wiring all tied back ip....with one additional for the LED conversion.


New caps. I just replaced the one bad one and its mate next to it....I left the rest alone.


Reassembled and testing..............

RF out = functioning again!




Now to test the composite:






I didn't bother testing the TV92 beyond powering up, as I don't have a CRT TV with schematics to properly test it.....and its probes & leads are still hiding somewhere. It's not a piece that would ever really be used again.... The VG91 with the pattern generator would still be useful even today.

[Topcat]

Re: Topcat's Dream Service Bench Reborn!

Nifty 'official' use of one of these machines..... Fixed a TV for a friend of mine....



Part of me really misses working on this stuff!