Salvaging useful parts from Old Stuff. What is useful?

[Wardy]

I have been slowly collecting a variety of tubes for my builds and now have a reasonable supply of Mullard, Ratheon, RCA, Tungsram in Ecc83, 82 and 81.

I wanted to try some telefunken but couldn't find any at reasonable cost. After some research I had a punt on a "for parts not working" Tape machine and bingo it had 8 telefunkens inside which are now in my collection ready for use in guitar amps. The machine looks like it might yield other useful parts. However it also looks in reasonable condition and could be fixed or restored by someone who is in to this. So my dilema is whether to strip it down further or to move it on as it is. I've a couple of pics attached. what do you think? Strip down or move on? anything of great use in a tube amps here? or is it sacrilege to destroy it?

[kagliostro]

I dismanted some old radio and reel recorders

No one was in good shape as the unit you show in your pdf

The parts you can save are tubes and Transformers

As radio and tape recorders aren't High Power units this Transformers can be used for small SE amps in order of 2 - 5 W of Power

Sometime you can find Stereo Units and so you can have under hand what can be used to relize a small Stereo Guitar Unit

Electrolitic caps ... to save them Isn't a good idea, way better to buy new ones, the old ones are prone to easily give you problems

Other components you can try to save are other kind of capacitors, this usually you find electrically  usable BUT they will result to have very short rheophores when gutted, practically unusables

Resistors don't wort the effort if you don't require one to perform an old equipement restoration

So ... what to do with your unit ....

If you find someone interested sell It as Is, only if you don't find any one interested recovery the PT and OT (for a very small project realization)

Franco

[Wardy]

Thanks for the advice Franco

[dogburn]

I'd check on ebay to see how much people have paid for that model in the past and then list it for cheaper as "for parts/not working" (like how you bought it) if it seems you could get a decent amount (like more than $50).

But if not, other than what Franco said, you maybe could save the tube sockets, and I'd think about saving the motor - that could also be sold to people restoring a similar model tape machine (as long as the motor works).

[Wardy]

That sounds like a good plan,

I don't know if the motor works. It was advertised as powering up but not turning. I guess I could apply an appropriate voltage to the motor to see if it works.

[kagliostro]

Years ago some people used reel tape motors to build custom turntable plates

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Which Is the brand and model of the reel recorder ?

Franco

[Wardy]

It’s a Tandberg 64x

[Platefire]

I've done a lot of conversions over the years. Reel to Reel recorder/players, projectors that would playback audio, PA Heads and mono Hi-Fi amps. The first thing I look at is, does it have a chassis that could be re-used or mounted in a DIY head cab. Are the tube types those normally found in guitar amp.The existing tubes in an amp usually dictate what your transformers can handle and what kind of guitar circuit you can use it to build. So if there is no re-usable chassis you are just about left with parting it out for another build. Several times I've spliced bits of metal plate to an oddball chassis to make it work. Usually on these old conversion projects, you get rid of everything that don't say guitar amp:>)

BTW---I didn't see any chassis on the two pictures you posted. Is there a chassis?

I always like to show this Revere reel to reel conversion as an example of utilizing everything possible on the old amp your converting-- R2-D2

[tubeswell]

What the others said. Power transformer, output transformer, and the audio tubes (that go with these*)


* make a note of which type of tubes came with the original unit. The tube datasheet for each type of tube will tell you the current that each tube’s heater filament draws. Add these up (where the heaters have been wired in  Parallel) and you will have the current rating for the PT heater winding. This is handy to know if you want to use more conventional audio tubes (if your unit didn’t already come with types of tubes normally found in a guitar amp).


https://frank.pocnet.net/

[Wardy]

Many Thanks Tubeswell,

I was trying to work out what I might be able to run off the transformer. I have a schematic of the recorder which shows the transformer has following taps.
Mains in. Multi voltages selectable from 110v to 245v. It says the power input is 65watts. There are three outputs. 245v/245 fused at 200ma. all the tubes apart for 2 used for indicators are fed from a 25v tap. fused at 2A and the 2 indicator tubes are fed from . 6.3v at 2A.
The heater circuit is strange at 25v.
Not sure what power the 245v tap would supply given the 200ma fuse but maybe at least half that?

[kagliostro]

How to know the power ratings of the winding of the PT

The HT winding:

Consider that tubes like ECC83 will absorb around 1.5mA each, ECC81 and ECC82 around to 10mA

in your schematic you have 4 x ECC83 - 2 x ECC82 - 2 x ECC81 so a consumption to around of 48mA can be estimated

then there are 2 x EAM86, each one has a triode 1.5mA and an indicator say 3mA so a total of 9mA

48mA + 9mA = 57mA DC

More there is the Solid State circuit (don't know how to estimate the consumption)

But the 245V AC winding feeds also the motor of the recorder

give a measure to the AC consumption of the motor then multiply it for 0.6 to obtain the DC available current as B+ as you don't use the motor in an amp

So your available B+ current will be 57mA + (Motor AC consumption x 0.6) + (something for the Solid State circuit)


For the 25V winding:

You have 4 x ECC83 + 2 x ECC81 + 2 x ECC82

As per your schematic the tubes are connected in 4 rows of two tubes each

so the ECC8x tube heaters are for sure connected for 12.6V

at 12.6V the consumption is 150mA for each tube but, as told you ave it connected in series in pairs

so you have 4 rows that has a consumption of 150mA each, connected in parallel

150mA x 4 = 600mA

your 25V winding can feed 600mA


For the 6.3V winding:

The 6.3V winding feeds 2 x EAM86 in parallel, each tube consumption is 300mA so for tubes total 600mA

but you have also a pilot lamp that is feeded from that winding, the consumption of that lamp may be around 200mA or 300mA, read the exact consumption on the lamp or measure it

your 6.3V winding can feed an estimated 800 or 900mA of current


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Perform the measure to be precise but you have


HT winding can feed, at least, 60mA (plus the motor consumption to be reversed in DC from AC)

25V Winding can feed, at least, 600mA

6.3V winding can feed, at least, 750/800mA (control the consumption of the pilot lamp)


Franco

[Platefire]

Har! I took a look at the schematic. That is a complex monstrosity. Never did find where I could positively identify a output transformer, That's a hard one!

[SEL49]

This unit only has line level outputs. No speakers, so no power amps and no OTs. The tubes are the only things usable for a guitar amp.

[Platefire]

OK, Good! I'm really not going crazy after all 

[kagliostro]

A PT Is present and if recovered can be used

But I'll not dismant it if someone Is interested to have the recorder

Franco

[tubeswell]

I didn't look at any schematic - if there's no OT, then you'll need to figure out another way of making audible output power. The PT will be good for what kagliostro said.

[kagliostro]

May be you can recover on the cheap an old radio that has an OT and not PT (line feed) or has as PT an Autotransformer (that Is unsafe to be used as It don't offer galvanic insulation)

Franco

[Wardy]

I was thinking of taking out the transformer to try to use on a low power single ended amp that I have in mind for a future project. However the machine looks in really good condition so I think I'll check if the motor works and let the answer to that question inform whether to sell as is or take out the transformer. anything now is a plus anyway as I have the Telefunkens I wanted and they all work.

many thanks for all the advice.

[kagliostro]

I think that the 6.3v winding has enough current to feed and EL84 tube (750mA consumption) but verify the pilot lamp consumption

If you go for a 6V6 (450mA consumption) available current will be more than enough

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The 25v winding require you use a Preamp that uses at least a pair of 12.6v heaters tubes (or more to achieve a connection like in the recorder, current will be enough to feed 8 x 12a*7 tubes or a combination of 6.3v tubes like ef86, 5879 or 6ak5)

Franco

[dogburn]

You could also go for a 6AQ5 power tube in a SE amp.

[kagliostro]

Yes, and many others, 6P1P is a 9 pin version of the 6V6 tube or one other (double thetrode), the QQE 03/12 (sometime used in audio, with success)

or other small pentodes like EL95 and don't forget the various ECL8* triode/pentode

and many others that can be used

Franco

[Williamblake]

Take what you can. Give nothing back. If it is a tape echo restore it.

[Platefire]

Around my local area you use to could turn up old tube equipment in thrift shops, pawn shops, antique stores and garage sales occasionally. But now days it is very, very rare! Believe me I use to chase after that stuff like a hound dog:>) after a rabbit.  Here lately when I have sighted something that I might be interested in, they had it priced so high I couldn't go for it. It might be different in your area? I have quit actively going on the hunt for tube stuff but even at that I find myself unconsciously still looking out for something. Stuff like I would be interested in is accessible only by e-bay or other on line markets--and I don't have to tell you about the price of those!!

On second thought, I got more amps than I know what to do with