Philicorda 22GM751 - Reverb Missing

[pelaurendeau]

Hello everybody,
I just bought a Philicorda 22GM751. The guy who sold it to me, told me straight away than the reverb wasn't working, but everything else was ok. I didn't had time to open it when I was there and thought also than it could be just a bad component somewhere. But actually, the all spring tank is missing !
I had access to another (fully working) 22GM751 but there is nothing wrote on the tank (like Accutronics tanks).

So my question is, does anybody know the reference of the spring tank, or his impedance in/out, or more easily, what would be a good replacement tank ?

​​​​​​​Thanks !!

 

[JonSnell Electronic]

The tank is driven directly from the loudspeaker output on this model, through a matching transformer.
If you select a tank with a medium input impedance, say 800R, that should work fine.
Like this one; Reverb Tank Short 3 Spring Medium Decay 8EB2C1B Guitar Tube Amplifier 800 ohm | eBay

 

[Mark Tillotson]

The tank is driven directly from the loudspeaker output on this model, through a matching transformer.

That sounded most odd, so I looked up http://modularstudio.nl/docs/PhilicordaGM751.pdf and its true - one speaker amp drives the tank, its output is routed to a different speaker + amp!

If you select a tank with a medium input impedance, say 800R, that should work fine.
Like this one; Reverb Tank Short 3 Spring Medium Decay 8EB2C1B Guitar Tube Amplifier 800 ohm | eBay

 

[pelaurendeau]

Thanks for the answers !

What about the output impedance ? Does it matter ? I'm not really good with electronic, but if there is a simple way to find the impedance with a VOM on the spring tank of the other Philicorda, I could try !

Also what about the connectors Insulated or Grounded ?

From what I saw on the other Philicorda, it look like a Type 9 spring tank but I have no idea about the decay if it's medium or long, so a 9EB2C1B or 9EB3C1B tank ?

 

[JonSnell Electronic]

Older machines used long delay tanks but it is only a matter of taste. Long delay tanks have longer springs.
Output impedance is of no consequence as there is plenty of gain on the pickup side.
The layout is as per the attached, for clarification.

 

[Bill Coltrane]

The ideal decay time depends on what you play.


Do you play long sustained chords, use a long delay.
Play stacato, short delay.




Spring reverbs are dirt cheap, diy a switch and you can use several spring reverbs.

 

[Kay Pirinha]

These reverberation tanks were proprietarily made by Philips for their Philicorda's. They can't be compared to any tank from Accutronics/Belton/Gibbs/Hammond, as they're longer than the short ones, but shorter than the long ones we all know. Maybe 8" to 10" long. And they're open frame, not in a closed can like the Accutronics.


Unfortunately my own Philicorda is stored away, and I don't have the time at the moment to go there, open it and shoot some pics or do measurements .


Best regards!

 

[pelaurendeau]

These reverberation tanks were proprietarily made by Philips for their Philicorda's. They can't be compared to any tank from Accutronics/Belton/Gibbs/Hammond, as they're longer than the short ones, but shorter than the long ones we all know. Maybe 8" to 10" long. And they're open frame, not in a closed can like the Accutronics.

That's what I was afraid of .. The tank seemed a bit different to what I'm use to but I thought and hoped the way it's suspended was the only thing really different ..

Well I guess, either I find a dead Philicorda somewhere or I'll have to go for a not original tank and hope it's not to far from the original..

 

[32860]

I know that both in the Philips Radio B7X43A (yes, with reverb...) and other Philips Radio's with reverb and 800 Ohm loudspeakers, a Gibbs Type 4 Tank was used. The Gibbs Type 4 Tank was also used in the Philips AG7600 organ amplifier, wich also has 800 Ohm loudspeakers.

Years ago i noted down that the Gibbs Type 4 Tank has the following spec's:

Impedance input = 1475 Ohm
Impedance output = 2575 Ohm

Rdc input = 182 Ohm
Rdc output = 183 Ohm

But i don't know anymore from where i got the impedances. The dc resistance however, i measured myself.

I see in the schematic of the 22GM751 that the tank is driven from the output through a step up autotransformer. This to me is an indication that the tank has a relative large input impedance.

In the Philips radio's with reverb and 800 Ohm speakers and in the AG7600 the tank is driven from the 800 ohm secondary of the output transformer.

Greetings,
Robert

 

[Kay Pirinha]

Hi,
is your Philicorda this model?
Today in the afternoon I've dismantled mine to get some pics for you. I saw that my memory really didn't serve me well as the reverberation tank is more huge than I've been remembering. It is about 44 cm long!
I also measured the resistances, but without disconnecting the unit. I don't know the schematics, so the values of the disconnected unit might be others. The driver measures 4 ohms, the receiver 180 ohms.
Btw, dismantling and reassembling a Philicorda is a real PITA! One doesn't want to do it more often than necessary !
Best regards!