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Toshiba sa-500 receiver



 
 
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  #1  
Old July 9th 08, 04:34 AM posted to alt.collecting.8-track-tapes
carfreak
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Posts: 7
Default Toshiba sa-500 receiver

I was recommended to go here by rusty . I am new to vintage audio,
and recently got a toshiba sa-500. It has a pretty bad balance
issue. I have to turn the knob to 3 on the right for it to be
balanced. Any solutions?
  #2  
Old July 9th 08, 09:22 PM posted to alt.collecting.8-track-tapes
DeserTBoB
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Posts: 3,541
Default Toshiba sa-500 receiver

On Tue, 8 Jul 2008 20:34:35 -0700 (PDT), carfreak
wrote:

I was recommended to go here by rusty . I am new to vintage audio,
and recently got a toshiba sa-500. It has a pretty bad balance
issue. I have to turn the knob to 3 on the right for it to be
balanced. Any solutions? snip


First, swap the speaker leads and see if the trouble follows the
speaker. You may have a loudspeaker issue, not an electrical issue.
If the trouble doesn't follow the speaker, you could have a number of
different problems, a likely one being a toasted output transistor,
which would make the channel in question about 6 dB less loud than the
good one. You don't say if the affected channel has a distortion
problem or not, which could alos be an indicator.

These weren't very good units, so don't go spending a lot of money
fixing it. Toshiba's audio products were, around that time, discount
store stuff at best. Their cassette decks were some of the worst I've
ever seen at any price.
  #3  
Old July 9th 08, 10:20 PM posted to alt.collecting.8-track-tapes
Rusty
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Posts: 34
Default Toshiba sa-500 receiver

On Jul 9, 1:22 pm, DeserTBoB wrote:
On Tue, 8 Jul 2008 20:34:35 -0700 (PDT), carfreak

wrote:
I was recommended to go here by rusty . I am new to vintage audio,
and recently got a toshiba sa-500. It has a pretty bad balance
issue. I have to turn the knob to 3 on the right for it to be
balanced. Any solutions? snip


First, swap the speaker leads and see if the trouble follows the
speaker. You may have a loudspeaker issue, not an electrical issue.
If the trouble doesn't follow the speaker, you could have a number of
different problems, a likely one being a toasted output transistor,
which would make the channel in question about 6 dB less loud than the
good one. You don't say if the affected channel has a distortion
problem or not, which could alos be an indicator.

These weren't very good units, so don't go spending a lot of money
fixing it. Toshiba's audio products were, around that time, discount
store stuff at best. Their cassette decks were some of the worst I've
ever seen at any price.


we did switch the speaker leads. that was the first thing we did. the
speaker was not the issue. the receiver has a lot of sentimental value
to my friend it belonged to his grandparents. how hard is it to switch
out the output transistor?

Rusty
  #4  
Old July 10th 08, 01:14 AM posted to alt.collecting.8-track-tapes
DeserTBoB
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Posts: 3,541
Default Toshiba sa-500 receiver

On Wed, 9 Jul 2008 14:20:57 -0700 (PDT), Rusty
wrote:

we did switch the speaker leads. that was the first thing we did. the
speaker was not the issue. the receiver has a lot of sentimental value
to my friend it belonged to his grandparents. how hard is it to switch
out the output transistor? snip


OK, this unit (I believe) has a speaker selection switch. Try running
from the "B" speaker terminals and see if the problem still stays the
same.

Replacing a standard TO3-case output transistor is quick work, but
first you have to know how to find the bad one. Tools would be a
soldering iron, thermal grease and normal screwdrivers, side cutters,
et al. I really don't have the JEDEC number of the original outputs
on those handy, but suffice it to say that, if failed, the bad
transistor won't be shorted, since the amplifier is still operating.
I'd look for oxidized connections on the output transistor heat sink.
Also, be aware that Japanese electronics from this era were well known
for developing cracked solder on their wave-soldiered PC boards, but I
don't think that's the issue here.
  #5  
Old July 10th 08, 05:52 AM posted to alt.collecting.8-track-tapes
carfreak
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Posts: 7
Default Toshiba sa-500 receiver

On Jul 9, 5:14*pm, DeserTBoB wrote:
On Wed, 9 Jul 2008 14:20:57 -0700 (PDT), Rusty

wrote:
we did switch the speaker leads. that was the first thing we did. the
speaker was not the issue. the receiver has a lot of sentimental value
to my friend it belonged to his grandparents. how hard is it to switch
out the output transistor? snip


OK, this unit (I believe) has a speaker selection switch. *Try running
from the "B" speaker terminals and see if the problem still stays the
same.

Replacing a standard TO3-case output transistor is quick work, but
first you have to know how to find the bad one. *Tools would be a
soldering iron, thermal grease and normal screwdrivers, side cutters,
et al. *I really don't have the JEDEC number of the original outputs
on those handy, but suffice it to say that, if failed, the bad
transistor won't be shorted, since the amplifier is still operating.
I'd look for oxidized connections on the output transistor heat sink.
Also, be aware that Japanese electronics from this era were well known
for developing cracked solder on their wave-soldiered PC boards, but I
don't think that's the issue here.


My receiver hasn't been used in probably over a decade, so oxidation
is very possible. I will check it out, thanks for the advice. If I
do find oxidation, how should I clean it?
  #6  
Old July 10th 08, 05:20 PM posted to alt.collecting.8-track-tapes
DeserTBoB
external usenet poster
 
Posts: 3,541
Default Toshiba sa-500 receiver

On Wed, 9 Jul 2008 21:52:35 -0700 (PDT), carfreak
wrote:

My receiver hasn't been used in probably over a decade, so oxidation
is very possible. I will check it out, thanks for the advice. If I
do find oxidation, how should I clean it? snip


On wafer switches, the best first aid is simply exercising them. For
noisy switches and pots, a switch contact cleaning spray, notably
those from Caig Laboratories (Caig Pro Gold is a favorite of mine), is
best, but don't overdo it. Washing potentiometers and switches too
much will wash out all the "pot grease" and the oxidation will return
shortly, along with erratic performance.

Also of concern, if the unit has been sitting around unenergized, is
the condition of any electrolytic capacitors in the unit. Usually,
this will manifest itself in "crackling and popping" noises, if the
power supply electrolytics are bad. Most of the older Japanese
receivers of this ilk used Nichicon axial electrolytics in for stage
decoupling, and they do tend to go bad. Job 1 right now, though, is
tracking down why one channel is performing badly. Good luck with
that.
  #7  
Old July 10th 08, 08:13 PM posted to alt.collecting.8-track-tapes
trippin-2-8-track
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Posts: 365
Default Toshiba sa-500 receiver

My receiver hasn't been used in probably over a decade, so oxidation
is very possible. *I will check it out, thanks for the advice. *If I
do find oxidation, how should I clean it?- Hide quoted text -

- Show quoted text -



carfreak check your email, I sent you one
  #8  
Old July 12th 08, 10:05 PM posted to alt.collecting.8-track-tapes
AntiNudo
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Posts: 27
Default Toshiba sa-500 receiver

carfreak wrote:

I was recommended to go here by rusty . I am new to vintage audio,
and recently got a toshiba sa-500. It has a pretty bad balance
issue. I have to turn the knob to 3 on the right for it to be
balanced. Any solutions?


it sounds like that there is a problem in the signal path like a resistor
that has opened up or a dried out electrolytic capacitor. i don't think it
is a output stage problem.

here is the best place to go to get help with your vintage Toshiba.

http://audiokarma.org/forums/forumdisplay.php?f=13
--

 




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