Author Topic: Philips Philicorda 22GM752 - What would cause a weak and distorted output?  (Read 150 times)

Offline DB-Keys

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I have recently acquired a Philips Philicorda 22GM752 which upon powering up was found to have a few issues, many of which I am pleased to say I managed to resolve. The vibrato wasn’t turning on when its switch was engaged, neither was the reverb, most of the switches were intermittent, a number of the keys were prone to getting stuck down, and some of the keys failed to produce any sound. A few squirts of Deoxit d5 contact cleaner on the switches soon sorted those out and I found that the vibrato issue was caused by a couple of breaks on the solder joint on the circuit board where the rocker switch was attached but reflowing the solder at these point managed to fix this and the vibrato effect was back working again. Also, the spring reverb suddenly sprung (no pun intended) back to life, probably due to the contact cleaner working its magic on the switch.

I then removed all of the keys and gave them a thorough cleaning as a large amount of gunk had built up between the keys over the years which is why they were sticking and not returning back up to their original resting position. I also gave the key contacts a gentle clean and once reassembled the keys were no longer sticking and the only keys that were now failing to produce any sound were all of the F# notes across the keyboard which I assumed to be an issue with the oscillator for that particular note which what I intended on focusing on next. Ok, so far so good. I seemed to be making progress with the only issue now remaining being the dead F# notes across the keyboard and so after having the Philicorda powered up and performing well for a good few hours I powered it down for the night with plans of investigating that F# oscillator the following day.

However, when I next powered up the Philicorda I found that the audio output was now extremely weak and distorted on all keys and barely audible at full volume despite full glorious sound just the night before. I have since checked again inside, looking for any loose/broken wires, bad solder joints etc and can’t seem to detect anything obvious. I have also tapped around with a wooden utensil on the various wires, circuit boards, components etc while the unit has been powered up and with keys pressed to see if that reveals anything but so far nothing has revealed itself.

Has anyone here experienced a similar issue with their Philicorda or know what may have caused such sudden loss in the audio output? Any insight or suggestions would be greatly appreciated.
« Last Edit: November 18, 2020, 09:47:12 PM by DB-Keys »

Offline Alan Lenhoff

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Re: Philips Philicorda 22GM752 - What would cause a weak and distorted output?
« Reply #1 on: November 19, 2020, 12:57:40 PM »
I would check the output of the power supply to see whether it's providing the proper voltage. In old instruments that have been sitting idle for years, it's not uncommon for the power supply capacitors to work fine for a short time -- and then suddenly fail. If the caps are original, they are decades beyond their typical lifetime.

Alan
Co-author, "Classic Keys: Keyboard Sounds That Launched Rock Music"

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1965 UK Vox Continental;1967 Gibson G101 organ; 1954 Hammond B2; Leslie 21H; Leslie 31H; 1974 Rhodes Mark I Stage 73; 1972 Rhodes Sparkletop Piano Bass; 1978 Hohner Clavinet D6; 1968 Hohner Pianet N II; 1966 Wurlitzer 140B; 1980 Moog Minimoog Model D; 1977 Fender Twin Reverb; Vox AC30CC2X amp.
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Offline DB-Keys

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Re: Philips Philicorda 22GM752 - What would cause a weak and distorted output?
« Reply #2 on: November 19, 2020, 03:05:36 PM »
I would check the output of the power supply to see whether it's providing the proper voltage. In old instruments that have been sitting idle for years, it's not uncommon for the power supply capacitors to work fine for a short time -- and then suddenly fail. If the caps are original, they are decades beyond their typical lifetime.

Alan

That would make sense and it appears that the capacitors are original so I guess that there will be no harm in replacing them anyway. The power supply capacitors that you are referring to, are these located on the rear board as shown here in an image that I manage to find online?

Offline Alan Lenhoff

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Re: Philips Philicorda 22GM752 - What would cause a weak and distorted output?
« Reply #3 on: November 19, 2020, 04:26:43 PM »
I've never actually seen a Philicorda organ in person, so I'm not a good source for you. (It certainly looks like a power supply, however, but other functions may also be included on that board.)  Perhaps it would be best if you asked this question on a combo organ site, such as https://groups.io/g/combo-organ . They do have some Philicorda owners who post to the site.

If you don't have one, you can download a schematic here: http://peel.dk/Philips/Philicorda_GM-752.html

Alan
Co-author, "Classic Keys: Keyboard Sounds That Launched Rock Music"

Learn about the book: http://www.classickeysbook.com/
Follow us on Facebook: www.facebook.com/ClassicKeysBook/

1965 UK Vox Continental;1967 Gibson G101 organ; 1954 Hammond B2; Leslie 21H; Leslie 31H; 1974 Rhodes Mark I Stage 73; 1972 Rhodes Sparkletop Piano Bass; 1978 Hohner Clavinet D6; 1968 Hohner Pianet N II; 1966 Wurlitzer 140B; 1980 Moog Minimoog Model D; 1977 Fender Twin Reverb; Vox AC30CC2X amp.
(See the collection: https://vintagerockkeyboards.com/ )