Tube Phonograph - Amp Conversion

[Chummy]

Hello I am new to the forum here. Nice forum by the way. I am new to all this so please bear with me.

I am a Harp player and have recently purchased a early 1960's Telefunken phonograph with tube amplification ( I reside in Germany). I would like to convert it into a small amp however I lack the knowhow and do not want to make any mistakes or injure myself in the process. Here is as much of the technical data I can offer at present as the unit is not yet in my posession. Tubes: ECL 82, ECL 82, ECC 83. Dual voltage, 110 + 220 Volt. Here are some photos to give you all an idea of what I am up against - http://bruzbluz.multiply.com/.

Does anyone out there have any experience with this kind of coversion? I have seen and read about people making old tube radios into bedroom amps however I have not been able to locate any DIYers in the net.

What I like about the whole thing is that it is compact and has room for a ton of ideas i.e, one 8" speaker and making the side speakers into mic and harp cases. I do however want to keep this a bit quiet as I live in a house with four other families in it.

Thanks in advance for any advice you all can provide.

Chummy

[Regis]

Ha, I have a few of those kind of conversions, they are cool. I am about to convert an old Voice of Music amp into a tween Champ.

It was hard to tell from your pics, but it looks like one of those amps that use a 30C5 output that has AC voltage on the tubes without any transformer in between. Is there a schematic inside the cab? What is the tube compliment?

You have to be careful if it is that kind of amp, you can get electrocuted.

[Arthur B.]

From your descriptions and what I see, the phonograph amplifier seems to be a stereo single ended design with a common power supply. The ECC83 is two voltage amplification triodes in a single glass envelope. The ECL82 is a voltage amplifier triode with a loudspeaker pentode, also in a single glass envelope. I don't know what modifications to make, since I'm not a harp player.

[Rob Mercure]

Chummy,

As I seem to see two output transformers at the left of one of the images I assume that this is a stereo phonograph? If so, then have, for all practical porpoises (and most are 'cept that silly Flipper fellow), two separate - three stage - low wattage (4-5W) amplifiers that can be converted. This is good cuz you can use one amplifier and, assuming that both currently work, have a complete spare set of tubes for the other.

Conversion will consist of assuring that you have a safely grounded and fused power supply, probably replacing the electrolytic capacitors, installing input and output jacks that match your specific application (most of us use 1/4" - PL55s - for both), and probably "moving" the tone controls so that they affect a different part of the musical spectrum (your treble control probably affects frequencies so high that only the harmonica's harmonics would be affected - for instance). I believe that there is a FAQ concerning conversion of PA amps to guitar amps floating around this board so you might want to search for it.

A good place to start - and to get your "feet wet" in electronics - is to take the time to draw out a circuit diagram of the amplifiers. But you only have to do one as I'm sure that both channels are identical. While this might seem daunting remember that there are only three valves on each channel - two triodes and one pentode - so you could just draw them in on a large piece of paper and then fill in the specific components as you determine them.

Lotsa luck

Rob

[Chummy]

I am still here guys!!

Thank you so much for the advice though contradictory at times it is a start. I will not complain as all information is good information especially when you do not know what you are doing. What does come up in all answers to my question is safety when working with these kinds of things and I will go forth with my work with that in mind.

I will make a circuit diagram - it will be my first so don't laugh if it looks like it is 3 meters long - haha. I have to hit the books on this one - I am lightly salted but not yet seaseoned. It seems to me that it may turn out to be a fun project with many variables in its outcome. I just want to enjoy myself dong it.

As soon as I find out more I will post.

Thanks again!!!

Chummy

[Rob Mercure]

Chummy,

I'm not sure that the advise really contains "contraditions" - I suspect that Regis didn't notice the valve designations you'd included and/or wasn't familiar with the european (or one of) coding scheme that denoted the first "E" as a 6.3 volt heater. Line connected - those sets with no power transformer and the tube heaters connected in series across 110-120 VAC were common on this side of the pond. I suspect there only reason that they weren't more commonly used on your side is the commonality of 220 VAC circuits (harder to create a 75mA heater string from the 150mA types which you'd have to do to duplicate the "All American Five" type of AC reciever circuit). But it is obvious that there are three transformers in the picture. And as best I can tell there is no contradiction nor disageement between Arthur's post and mine.

Anyhoo, let us know how your project fairs.

Rob

[Regis]

Chummy,

I'm not sure that the advise really contains "contraditions" - I suspect that Regis didn't notice the valve designations you'd included and/or wasn't familiar with the european (or one of) coding scheme that denoted the first "E" as a 6.3 volt heater.

Yah, thats right, sorry.

[Chummy]

Sorry fellas if I sounded like I was bashing you. I didn't intend it that way - I just don't know what I am doing yet but will by reading your mails. You guys are the pros. I do not think you know how helpful this is.

Thanks trainloads!!!

So it doesn't look that bad for me then. I will have to get in touch with a techi here and see what he says as well. It is hard for you guys to work from pictures and no real factual information but if you get a wild hair let me know. I will post my findings as I go as this is an interesting project.

All american five?

Take care and do good,
Chummy

P.S. I am an American - originally from Minnesota. I have been in Der Vaterland for almost 20 years now. Homesick after all these years too.

[Rob Mercure]

The "All American Five" was a five tube series heater string line connected AM radio design that went through two distinct phases, Octal and Miniature (and there was Locktal one as well). It consisted of a pentagrid converter used as an RF and and mixer, a pentode IF amplifier, a triode/diode first AF/detector, and a beam power tube output as well as a rectifier. All the tubes heaters in series added up to 110 volts, or so, and usually drew 150 mA - although there were other variants. Usually the first three tubes had 12V heaters while the output tube was a 50V unit and the rectifier a 35V valve.

At the last of the "reign of tubes" when SS rectifiers became common there were "strange" variants of the overall circuit using four tube with 18 V and 36 V and 60V heaters but these didn't last long.

Rob

[rocket]

In Europe there are the "P" tubes designed for 300mA series heating, mainly used in TVs, where lots of tubes were required. "U" tubes (series, 100mA) are sometimes used in PT less radios.