Test PROM for Philips PM5390S

[giosif]

Hi,

I am trying to repair a PM5390S RF synthesizer and the manual mentions a test PROM which allows one to do several checks.
Does anyone here happen to have this PROM available and willing to share, please?
A Google search didn't reveal anything useful.

Thanks!

[Emo]

Hi Giosif,

I did a repair and upgrade on this synthesizer some years ago. Unless the processor or keyboard is at fault I don't think you will need the prom. In chapter 7 of the service manual a detailed checklist will bring you a proper working instrument.
In my unit a lot of electrolytics inside the closed synthesizer unit were bad.
Originally my unit was a regular one and using the included print layout in the service manual I build the power amplifier myself, power supply already being prepared for that, so now i have the -S version. The altered software can be switched by jumper.

Eric

[giosif]

Hi Eric,

Fair enough.

Two other questions, if I may:
1. Do you know how to remove the plastic cover of the power button?
    Step 2 in section 4.6 of the service manual says to do that in order to get the keyboard/display unit out, but I'm not sure how and I would like to avoid breaking any plastics.
2. What did you replace the SRAM battery with?

Thanks!

[Emo]

Hi Giosif,

The chrome plated outer ring on the power supply switch is actually a nut in disguise. So carefully gripping it with pliers and some protective material in between you can screw it of.
The SRAM battery can be switched on and off by the jumpers on the back. It contains three NiCad cells that will be charged during use. Any 3,6 V model will work. In my case some life was left in them so I was lucky. Working without is no issue as it only stores the presets.
And this is where the magic happens inside the closed box

[giosif]

Thank you, Eric!

I eventually unscrewed that ring, although it wasn't as simple as gripping it and turning it counterclockwise.
With regards to the battery, I am evaluating the options, as I am reluctant to install any NiCd / NiMH batteries which might leak at some point.
I eventually mustered the courage and opened the big & heavy box and, funnily enough, checking the electrolytic caps in there, almost all of them had less than half their rated capacity, although their ESR was ok. 
I replaced the caps and re-assembled the box.
On to the display unit now...