Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: swingarm on November 19, 2021, 01:03:56 pm
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Hi all,
I am building a supro 1605r and have signal all the way to the input of the Paraphase inverter. Same values as the 1624.
I'm getting no sound. I''m using 5cz5's for power tubes with 330 volts on the plates and 289 the screens. What might the problem be?
Any ideas?
Thanks
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I am building a supro 1605r and have signal all the way to the input of the Paraphase inverter. Same values as the 1624.
I'm getting no sound. I''m using 5cz5's for power tubes with 330 volts on the plates and 289 the screens. What might the problem be?
Any ideas?
Hard to be specific without a schematic and your voltage readings. So generally speaking, the problem could be between the PI input and the speaker.
PS... I just saw your previous thread about the 1650r. Did you ever locate a schematic? How can you build one if you don't have a schematic?
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I did find it yes :) I put in an effects loop you posted in the effects loop achieve thread. The donar amp is a Fender Ramparte I got a super deal on.
I'll post the schematic.
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Can you also show us some hi-rez pics of your build?
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I will include a partial layout and few shots. It's a very compact build.My apologies for the less than stellar pics. I included the effects loop later after the layout. It's between the volume control and the PI.
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I'm glad I don't have to work inside that narrow chassis. I can't tell anything from the pics. One question though, what's the MOSFET for?
I included the effects loop later after the layout. It's between the volume control and the PI.
And that's where you say you lose the signal? Put a patch cord between the EFX jacks. Any better?
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I have good signal after the efx loop. The mosfet is part of the regulated screen supply it keeps the screen voltage around 300 or lower (adjustable). I have a ss rectifier switch too. Just kinda frustrating and yes this will not be a fun amp to service :)
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What tube type is your PI?
Looking for clues...
Measure plate, grid, and cathode voltages for BOTH PI triodes.
Measure grid and cathode resistance to ground for BOTH PI triodes.
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...I'm getting no sound....
Stick your head in the speaker. No sound? Or NO!! sound? Not a trace of hiss or hum?
If truly silent, suspect miswired speaker circuit. OT wires, jack, plug, wire, speaker.
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I took Sluckey's advice and bypassed the efx loop. I now have an awful ground issue noise. it's like motorboating at at least 1000rpm lol
PRR you are right, I wasn't quite as articulate in my description as i should have been. I had a very faint signal coming through the speaker and a very faint ground type hum that was amplified to the extreme when i bypassed the efx loop. A signal does exist under that awful noise.
Tomorrow is another day.
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tube type 12au7
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Hi swingarm!
I know this is an old threat ….
But I’m on the market for a low wattage amp, I love the 1605r either new one(I like the line out features), or I being able to build one, so thanks for the inspiration.
Right now I’m on researching the possibility of building one.
Can you please share more details of your build?
Which transformers models did you used?
I have seen old versions loaded with a 10”, new ones are 8”. Did you fit it with a 10” or with an 8” speaker? Which one?
I really like the form factor of the 1605r, did you build the cabinet yourself on the same form factor? Or reuse and old housing?
From the schematics of the new one, these seems to be the reverb tanks they are using.
https://www.amplifiedparts.com/products/reverb-tank-mod-8fb3c1b-long-decay-3-spring
Did you stick to that one?
I still need to understand better the schematics(either old or new one with fancy features)…but I’m working on it. Did you tweak the amp to your liking? Which are the most likely tweakable parts to individual taste?