R2600 Power supply shuts & RF input temp warn

[bigbop]

I have an R2600 where the power supply will start for an instant then shut down.
It sometimes will stay up for a minute but then I see the RF input overtemp alarm appear.

I've replaced all the electrolytics on the power supply board and that seemed to fix the issue but then it returned.

I rigged up an adapter cable and I'm running the unit from a PC supply but I'm not powering the +40V line.
Anyone know what +40V is used for on the R2600? Seems like an odd voltage. Bias voltage for something?

In any case, the unit powers-up on the PC supply but I'm still getting the RF input over-temp alarm.

Any info on the power supply board and RF over-temp issues would be greatly appreciated.

Thanks.

[jry]

I would inspect ALL of the electrolytics on the boards especially the 25uf SMT for leakage.
My guess is that you are over currenting the original supply with one of those caps starting to short.
The PC supply may have a higher current threshold and that is why you are staying up but seeing errors as a supply rail intermittently dips

Be cautious with another supply since you may end up burning up boards and connectors ( voice of experience on that one )

It's a real PITA since those caps are used everywhere down to the RF I/O module and it's a million screws

[bigbop]

I borrowed the power supply from another R2600 and the unit worked without the ref input temp errors and without any shutdowns.

Do you know off hand what the +40v supply is for?

If anyone has the schematic for the power supply they could share, that would be a great help.

One last but of info - the unit will NOT run from a 12v supply if that helps with the diagnosis.

Thanks

[jry]

would test the defective power supply stand alone and use the 12VDC input to minimize the shock risk. Jumper the bottom two pins ( toward the PCB edged ) on the output connector for power on.
One of the pins should be at around 11vdc and the other brings the supply up
Before doing that I would check the output diodes for shorts/opens and also inspect the output caps and check for shorts there as well
Sounds like you may have something shorted in the output sections ...usually its the diodes.
The 40VDC is used for the synthesizers and is regulated down to 15 ( high synth) and 24 vdc ( low synth ) on the boards as a low noise supply to steer the VCO's
May be used elsewhere as well but I think those are the two main uses

The main regulator chips is a UC3825 but it sounds like that is OK ...the over current sense is detected differently between AC & DC and it fails on either input with what sounds like an over current which is why I suspect a problem in the output.
Good luck

[bigbop]

Thanks for the input. I just started to build an adapter cable so I can stick some loading on the various outputs. I've reverse engineered the output after the switching transformer and checked the choke and diodes and they seem OK. The +5v is sensed and I can see the current sense resistor. I changed all the caps as well.
Do you know off hand what would trigger the input ref over temp sense?

It would share help to have a schematic of the PS for this but I have a feeling I'll create my own shortly. It just seems strange that there are no redilly available service manuals like there is for my old R2012 analyzer.

[bigbop]

Yup, it's the supply. I built an adapter cable and stuck appropriate loads on the PS outputs and tried to run it from a 13v supply.
Looking at the outputs, I was getting about 1/3 of the rated voltages and the supply screamed, then died.
I pulled up a lead on all the recitifiers and tested them - they're good.
I scoped the transformer primary at the power FETs and the square wave was a mass of ringing. Looks like maybe a shorted turn.

I'm guessing the 40v also powers the RF input load temp sense circuit as well?

Is there such a thing as a rebuilt supply for these units that I can buy from somewhere?

Thanks

[jry]

the manual can be ordered from jdosher ...just google jdosher manuals and it should come up
The main loop is referenced to the +12 and there is an overvoltage detect on the +5 which can cause a shutdown similar to overcurrent.
if you have the supply running standalone you can lift the colector of the 5V overdetect output and see if that brings the supply up,
Does it show overtemp with a good supply ? If so then check on the Wattmeter assembly and see if it is sourcing the condition.
The full manual will help in isolating both

[bigbop]

the manual can be ordered from jdosher ...just google jdosher manuals and it should come up
The main loop is referenced to the +12 and there is an overvoltage detect on the +5 which can cause a shutdown similar to overcurrent.
if you have the supply running standalone you can lift the colector of the 5V overdetect output and see if that brings the supply up,
Does it show overtemp with a good supply ? If so then check on the Wattmeter assembly and see if it is sourcing the condition.
The full manual will help in isolating both

Thanks for the info.
Just before you posted this reply, I sent an email to jdosher inquiring about a service manual.
I had the RF input assy apart (A hundred screws!!) and checked the RF resistor pad but didn't see anything out of the ordinary.
I also pulled the modules (ugh - more screws) to inspect visually for faulty caps and everything was clean. (note to self - get an ESR meter)

This unit actually ran for about a week before the PS started failing. WHen I ran it from the PC supply, I didn't have a 40V source, and I'm thinking that is why I'm getting the RF input temp warnings every few seconds - probably the temp sens circuit uses the 40V in some fashion.

Ultimately, I'd like to replace the CRT with this LCD module I found on eBay:
http://www.ebay.com/itm/VGA-AV-signal-D ... 0877360368
That way the unit will have a full colour display.

[jry]

the CRT version R2600's are EGA output so you typically have to convert to VGA and the arcade game version converters will not handle this. A more upscale converter is usually needed.

The 40VDC is not used by the wattmeter module ...uses the _5,-12 and +12

[bigbop]

Well, there's always this board:
http://www.ebay.com/itm/CGA-EGA-RGB-VGA ... 0833084570
Team that up with a 7" VGA LCD and you're good to go...

You seem to know about servicing these beasts.
Which of these service manuals should I be looking at obtaining for my R2600B/HS?
RLN5237A, RLN4120, RLN4120A or RLN4120C

Thanks

[jry]

The GBS8200 will not sync on the EGA output from the R2600

The service manuals available are pretty limited so you may not have much of a choice anyway. For what you have the version available will cover the unit pretty well.

As far as I have looked the major differences in vintages is the processor board. options and display . A couple of RF modules had additional connections in the C & D for the later 2660 and 2670 options.
The display finally went color LCD/TFT and VGA out on the D vintage.

[bigbop]

JRY, thanks for the help here.
I've ordered the manual from J Dosher in the UK and he's sent the first 4 of 14 modules to me.