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I recently picked up 3 Webster Electric intercoms from the late 30's (I believe)
They're really heavy for their size and have big power transformers. They're all the same model: 212 CS
The tube complement is 6J7, 6F6, and 5W4 rectifier. I'd like to minimally change the circuit and turn them into guitar amps. I traced the schematic out by hand and was able to find the repair manual online which helped confirm that my schematic was right. It also told me that the internal speaker is 50 ohms which means that the output transformer will likely be all wrong for guitar.
I wrote the schematic out in the style of the Fender champ 5C1 because I wanted to easily see how it compared. It differs in some ways I find confusing. On the schematic I simplified some things like removing all the switches and relays for the intercom. there was standby switch which I disconnected for the time being
I removed the microphone transformer and connected the guitar input directly to the grid of of V1 (6J7). The ground on the jack connects to the bottom of where the mic transformer was (the .1 cap, 150K resistor)
This circuit is really confusing me. Any time I try to change the value of any resistor or capacitor following V1 I get a lot of distortion, high frequecy ringing and loud hum. I'm also getting a confusing grounding problem where when I hold my hands on the strings of the guitar it actually hums louder.
I'm considering taking all the components out and starting from scratch because the wiring is a real web and the solder connections are poor. In this case I would wire up basically the Champ 5C1 circuit. I definitely want to keep the tubes that I have in there? I don't know how to change the values for the 6SJ7 and the 6V6 for 6J7 and 6F6 although I've read that they are similar tubes.
I think I've gotten in a bit over my head, but the circuit seems simple enough I think I just need a push in the right direction.
thanks!
They're really heavy for their size and have big power transformers. They're all the same model: 212 CS
The tube complement is 6J7, 6F6, and 5W4 rectifier. I'd like to minimally change the circuit and turn them into guitar amps. I traced the schematic out by hand and was able to find the repair manual online which helped confirm that my schematic was right. It also told me that the internal speaker is 50 ohms which means that the output transformer will likely be all wrong for guitar.
I wrote the schematic out in the style of the Fender champ 5C1 because I wanted to easily see how it compared. It differs in some ways I find confusing. On the schematic I simplified some things like removing all the switches and relays for the intercom. there was standby switch which I disconnected for the time being
I removed the microphone transformer and connected the guitar input directly to the grid of of V1 (6J7). The ground on the jack connects to the bottom of where the mic transformer was (the .1 cap, 150K resistor)
This circuit is really confusing me. Any time I try to change the value of any resistor or capacitor following V1 I get a lot of distortion, high frequecy ringing and loud hum. I'm also getting a confusing grounding problem where when I hold my hands on the strings of the guitar it actually hums louder.
I'm considering taking all the components out and starting from scratch because the wiring is a real web and the solder connections are poor. In this case I would wire up basically the Champ 5C1 circuit. I definitely want to keep the tubes that I have in there? I don't know how to change the values for the 6SJ7 and the 6V6 for 6J7 and 6F6 although I've read that they are similar tubes.
I think I've gotten in a bit over my head, but the circuit seems simple enough I think I just need a push in the right direction.
thanks!
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