Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: daveyajd on September 28, 2015, 10:34:12 pm
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I happened across a 1940's Remler radio today in a thrift store. It looked promising and had a bit of weight so I figured at the very least it may have usable iron. I brought it home and I am optimistic after opening it up. I attached the schematic. It looks like an "American 5" style with a 6V6. If I am reading the schematic right the PT is 300-0-300. After taking a few measurements it seems to have about 370V on each pin of the 6X5GT. I am trying to trace and measure for 5v and heater voltage. This chassis is to small to be usable to me but I will use all the 8 pin sockets and salvage anything else. What if anything do you expert eyes see? Any ideas for a build with this PT?
Aaron
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So looking at this a bit more it looks like the 6X5GT uses pins 3 and 5 for HV (370v at each) and pins 2 and 7 are the heaters. So no 5v on this I will have to use Hoffman's filament tranny when I go to use this.
Aaron
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Use the existing PS and output stage. Graft your preamp to the PS and output stage.
---pete
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Great starting point for a fun amp! Back when I really knew nothing about amp building I converted a Newcomb phono with the 6X5GT rectifier into a 5E3. Very soulful. I used the chassis, tubes, transformers, and yes...the same rectifier. You could have a nice vibrochamp... or a 6v6 version of one of the AX84 variations. There is good info on this site about adding a resistor and second cap to the first node of the power supply to eliminate hum in a single ended amp. Hmmm, I'm getting too interested. I might have to watch for my own thrift store radio.
Craig
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Use the existing PS and output stage. Graft your preamp to the PS and output stage.
+1.
The 6SQ7 is like 1-stage of a 12AX7 in an octal package. But you could swap that tube with a 6SL7, add appropriate components, remove the 2 pentodes and RF/IF circuit, add a 1/4" jack; now you have a Champ-type amp.
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> This chassis is to small to be usable to me
> I will use all the 8 pin sockets and salvage anything else.
> no 5v on this I will have to use Hoffman's filament tranny
IMHO, this is a Wrong Path.
The radio IS an audio amplifier, and this is a better-than-average one.
It has a tuner too, but you have wire-snips, you can disconnect that.
The chassis is plenty big enough for a Champ-like amp. The whole radio is two bottles more than a Champ, and Remler's workers crammed it in.
The sockets were low-price junk in 1955 and have not got better with age. They are NOT worth drilling-out, de-blobbing, and re-using.
All the caps are shot and the resistors were about as cheap as would work for 30 days.
That 6V rectifier is as good as any small 5V rect.
_I_ would verify that it plays AM (or makes loud crackles as you try to tune something). That is, the power supply works and the audio path kinda-works. You may set-off a smoke-bomb as the old-old caps die, so try this outside. You already saw the PT make juice, everything else can be replaced, but we'd like to hear the OT work. If the speaker's coil has been gnawed by porcupines, clip-lead any handy good speaker on to it.
This needs about 0.25V at the Volume control for maximum output. Guitar can be 10X smaller. The instant answer is a booster pedal. The period-correct fix is to re-use the IF tube as an audio preamp.
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Thanks for the replies. I did verify some sound when I got it home. I could tune in a station but the output was minimal at full volume. (You would hear it playing next to your bed on a quiet morning but it wouldn't wake the kids up in the next room)
I have started pulling components out and removed the tuner. I'm sure that I could have wired in a 1/4" jack and a few components and gotten some sort of workable amp. But honestly, for me I really enjoy the fabrication of making an amp in a good looking, well laid out chassis space. Drilling out the chassis and making a face/back plate that presents my custom build well is a lot of fun.
I am going to remove the caps/resistors across the chassis leaving the PT and OT wiring untouched. Then I will decide how I want to put it all back together.
I am leaning toward a Champ type amp but I think I like the idea of using the 6v rectifier
The sockets were low-price junk in 1955 and have not got better with age. They are NOT worth drilling-out, de-blobbing, and re-using.
I actually salvaged some octal sockets like these from an old Bogen I had. I used them in my TOS build and I thought they worked just fine. Of course, I am a total neophyte at this so I honestly don't know any better.
Aaron
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Concerning 6SL7 tubes - they sound really warm and glassy - I really dig them. To make a Champ circuit with one as the input you would not be disappointed.