Reviving 50+ year old Wire Recorder

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My father has "bestowed" upon me the old family wire recorder, a Silvertone
Model 8170. He claims that the last time he ran it (a year or two ago) it
worked for a while and then smoke came out of it.

And now I have it.

I opened it up, blew all the dust out, reseated the tubes, plugged it in,
and it ran fine - except that the only sound out of the speaker was a strong
60 Hz hum.

For $20 I've ordered replacement tubes for it, seems like that's got a good
chance of solving the problem.

If not, do people have suggestions on how to "debug" this problem? I've got
an old oscillscope I can use.

It's got a schematic printed on the bottom of the case, but only about half
the schematic remains, and it's the half dealing with the microphone and
phono input, not the speaker output.

The only idea I have, is to take beast apart even more, and try to re-create
the schematic, or at least the speaker amplifier portion.

And then the next question - if I get this thing working (or even if I
don't), is there anything reasonable to do with it? It has some mild
sentimental value, not much, on eBay some of these are going for a whopping
$10, are there museums that might be interested in such a piece?

Thanks all!
Chris

 

The tubes are probably fine, you have some audio and tubes rarely just fail
unless the heater burns out, usually they gradually get weak. Any
electrolytic capacitors are likely dried out and will need to be replaced,
switches should be cleaned, and everything carefully inspected.

 

[snip]

You can also ask on rec.antiques.radio+phono. Wire recorders are
discussed from time to time.

Frank Dresser

 

If smoke came out, you should see some charring.

 

I'd actually suspect filter cap('s) in the power supply, or if it happens to
use selenium rectifier(s) in the ps, then those.

Ken

 

Selenium rectifiers make a very distinctive smell when they fail

 

Or dripping if the filter cap.

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Blech! Yeah they do! Is there anything that smells more horrible?

 

Oh yeah! If you've ever smoked one of these there's no way you're *ever*
going to forget that smell...

I wonder how many of you guys have worked on stuff that uses these?

 

What about those aka stinky rotten fish cans (caps) when soldering?
This made me really go oooh! snorting & hands waving trying to get
stink out of my nose every time. Is this like that for smoking
selenium rectifiers? Yes I did seen them but not ones that blew.

What about the blue disk caps that let out pall of BIG thick pink
smoke, somewhat stinky?

Cheers,

Wizard

 

Old tube circuits should be powered up slowly with a variac, so that
the electrolytics have a chance to reform.
Failing that, all electrolytics should be replaced before power on, as
it is extremely likely they are bad; that is why you heard hum. New
tubes will not fix that.
My questions are (1) do the e-bay recorders *work*, (2) are those you
found actually wire recorders?, (3) if they had been repaired, were as
orginal parts as possible used? (4) case, panel, knobs, etc in
semi-pristine condition?
I dare say *no* to most of that criteria.
You have a possible collectible, and the better the condition, and
original-type parts for repair used, the higher the value.
Oh, yes i forgot - any wire spools for recording? And what is recorded
on those you have? Any documented provenance concerning those recordings
(historical interest).

 

Yeah, *real* slowly, if you have the patience for that. And they may end up
turning out to not be any good anyway...

That "original parts" bit got my attention.

How can you even *get* "original-type parts" for a lot of this stuff? And why
would you want to, assuming that you wanted something to work?

Going back a couple of decades, I spent some time helping a guy get a number
of antique radios working. He was interested in anything that wasn't
plastic, most of it going back to WWII or before. I'd take the guts out and
work 'em over, get it working well.

For electrolytics a number of those sets had cans that had a *big* nut going
around a threaded bushing. I'd never seen those prior to working with those
sets. At that time, I had a few of those mounting plates for the twist-tab
type cans (and probably still have a couple) and I ended up drilling screw
holes, putting one of those in, and putting a twist-tab can in there.
These days I'm not sure those are even available.

And those old wax-coated paper caps! I always end up yanking them out and
replacing them with mylar types. There's little likelihood of them still all
being good after all those years.

Now, assuming that you could even _find_ original-type parts for these
things, would you really want to use them? Seems to me that would be just
asking for trouble...

 

Yes. When they fail inside a sealed, pressurized power supply housing,
and the dimwit pilot or EWO leaves it on for the whole mission (i.e.,
continuing to burn), and you open the power supply case in the shop.

It clears the room. (how do you do a yucchy-face with punct. marks?)

Cheers!
Rich

 

sounds like a paper capacitor smoked, could of caused a resistor or 2 to
burn as well,replace all the paper caps and check for bad resistors. a
schematic probably will be nessasary as the values on the parts will be
hard to read,might get lucky with schematic if its on inside of the cover.
the tubes are also a good idea, most are probably weak and in need of
replacement.

 

Hi. Sounds probably like a bad capacitor, or possibly a dud connection
on the input end of the audio chain. I'm not sure if youve got the
knowledge to do it but we can see.

Forget new valves, keep the old ones in there if poss. And keep the
scope off it as you may make the scope case live and get electrocuted.
Place to start is work out which valve does what, and try the unit
with different valves pulled out to locate the problem area.

Next move would be to replace any bad caps. But since this is a
valuable museum piece I wouldnt replace them, I'd open the caps up,
fit well rated modern ones inside and reseal exactly as per original.
And only on caps that test bad.

Dont dismantle unless you know what youre doing. Live voltages may
appear where you least expect them, eg on heads, knob spindles,
chassis, and stored in reservoir caps when the things unlpugged. I
would do as assessment of its safety before plugging it in, theres
some truly stuipid stuff around from back then.

Really though I'd give it to a specialist to assess if possible.


Regards, NT

 

AFAIK this is an *old* and maybe repeated posting, and has been
answered numerous times....

 

A serious 60~ hum is wonderful,tells you a near guaranteed filter capacitor in
power supply was the source of smoke being they were almost always electrolytic
(oil filled) and had a shelf life,value is printed on each one (just replace all
big metal cans or cardboard tubes,to use scope on tube audio eqp just connect both
chassis and probe away using right hand only,enjoy Bill

 

An oil-filled capacitor is *completely* different than an
electrolytic!
In tube equipment, the 250-450V plate supply is filtered with
electrolytic capacitors, which can age when not used.
Best way to try "re-juvenation" is to put the equipment on a variac
and s-l-o-w-l-y turn the voltage up from zero to full line voltage; some
will not recoup so need to be replaced.

 

Sounds like a good way for the inexperienced to electrocute
themselves. Cant recommend it.

A much more minor point - reservoir cap failure will in most cases
produce 100 or 120Hz hum. 50 or 60Hz more likely means a problem at
the audio input end.

Regards, NT