Hi
I'm looking for the schematics and if possible a kit to re-build a PP El34 amplifier. I have the chsis, tubes, power and output transformers from a Cadence (made in India) amplifier.
I have some experience in electronics and DIY projects, so the complexity wont be a problem.
Any idea how to start?
I'm looking for the schematics and if possible a kit to re-build a PP El34 amplifier. I have the chsis, tubes, power and output transformers from a Cadence (made in India) amplifier.
I have some experience in electronics and DIY projects, so the complexity wont be a problem.
Any idea how to start?
Welcome to the forum. I will move your question to the tube/valve section.
It would be good to show some pictures and write down some information about the components, schematic (if you have one etc.). That will help to find the best options for you.
Note:
Post # 1, He said: He Is Looking For the Schematic.
Without that, the Blindfolded Archer is trying to hit the bullseye on the target.
Post # 1, He said: He Is Looking For the Schematic.
Without that, the Blindfolded Archer is trying to hit the bullseye on the target.
Another Welcome! to the forum. If a published schematic isn't available, forum members can often decipher a lot of information from just a listing of the tubes in use (to guess the likely choice of circuit - there aren't that many in common use) and a few photos.
Be safe, have fun, and all good fortune,
Chris
Be safe, have fun, and all good fortune,
Chris
Thanks for the reply, I´m not at home now to take better fotos, but I had the following: one view of the whole amp, but with two modifications I was doing at that time: adding a 6SN7 preamp (which is in the top) and an automatic bias circuit (at the center behind the filters).
The second phot is the pcb for two EL34 tubes and the other two are the PCB of the one channel power source.
Unfortunately, there is not schematics available.
Hope this helps.
The second phot is the pcb for two EL34 tubes and the other two are the PCB of the one channel power source.
Unfortunately, there is not schematics available.
Hope this helps.
Attachments
No schematics, even of the modifications that you've done? You're not giving us a lot to work with. Is there an actual problem or fault with the amplifier, or or are you just generally interested in improving/ modernizing it? Either will require a schematic, which you can draw out for yourself, unfortunately by hand, the old fashioned way. Worst case.
All good fortune,
Chris
If it's any consolation, that effort is what the sergeants in the Army used to call "Good training, men, good training." Not fun while you're doing it, but sometimes options are limited. If you get lucky with a published schematic, you'll lose out on all that fun training 🙂
All good fortune,
Chris
If it's any consolation, that effort is what the sergeants in the Army used to call "Good training, men, good training." Not fun while you're doing it, but sometimes options are limited. If you get lucky with a published schematic, you'll lose out on all that fun training 🙂
For what is worth, the Eico HF-89 is a pretty simple, straightforward PP amplifier using EL34: https://www.manualslib.com/manual/887362/Eico-Hf-89.html
Thanks jcalvarez
Looks like I can do it, any advice about where to the look for the parts? Particularly about the capacitors?
Looks like I can do it, any advice about where to the look for the parts? Particularly about the capacitors?
I typically use 4 sources:
- Digikey/Mouser for capacitors, resistor kits, power/output transformers (I'm UK based, there are better options in the USA)
- eBay for NOS tubes (mostly from Ukraine suppliers), screws, chassis etc
- AliExpress as an alternative for resistors/transformers, also miscellaneous things like sockets.
- HotRox UK for Belton sockets.
For power and output transformers I'd say Edcor and Hammond are the best bet for quality that does not break the bank. The output transformer is, IMHO, the most important component of the amplifier, only second to the speakers.
If the cadence amplifier was defective to begin with, you can try writing the manufacturer to get a schematic.
You might try telling them that you are a qualified service technician and that you are repairing it for personal use.
You might try telling them that you are a qualified service technician and that you are repairing it for personal use.
When the system started with problems, few years ago, I wrote the manufacturer several times with out any success.
I knew that the circuit for automatic bias (which where encapsulated) was broken, in fact it was burned, and I was asking for the replacement part.
At that time I was able to adapt a potentiometer and get the amplifier to work, but little by little, other parts where failing.
Now with the adaptations the amplifier is working but is a mess and I can't eliminate the hum. This is why I want to rebuild the whole system using only the chassis (which is nice), the tubes and the transformers.
I knew that the circuit for automatic bias (which where encapsulated) was broken, in fact it was burned, and I was asking for the replacement part.
At that time I was able to adapt a potentiometer and get the amplifier to work, but little by little, other parts where failing.
Now with the adaptations the amplifier is working but is a mess and I can't eliminate the hum. This is why I want to rebuild the whole system using only the chassis (which is nice), the tubes and the transformers.
Can you draw the output stage schematic from the board? It would help to know how the EL34s are connected, pentode, ultra-linear or triode mode. Also measure the output transformer ratio to get the expected primary impedance.
Thanks huggygood, this is the same amplifier and the similar problem, but I don't see a final advice in that trend
Is this link helpful jcalvarez? I think the EL34 are in triode mode.
Is this link helpful jcalvarez? I think the EL34 are in triode mode.
I love EL34s in Triode mode;
but I love KT77s in triode mode even better . . . just a shade better performance of: power and distortion.
but I love KT77s in triode mode even better . . . just a shade better performance of: power and distortion.
I'd say any link supplying extra information is helpful, even if there are no conclusive findings 🙂
Personally, I'm a big fan of ultra-linear for push-pull and triode for single ended. If I had to choose between pentode mode and triode for push-pull, then the choice would be always triode.