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AFAIK this is an *old* and maybe repeated posting, and has beenChris Cooper wrote:
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
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
Chris Cooper wrote:
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
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
An oil-filled capacitor is *completely* different than anA 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
"N. Thornton" wrote:
Chris Cooper wrote:
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
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
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