I wish I had this on the bench in front of me.
Try it with a speaker... without a scope its as good a clue as any as to what may be going on. Keep the volume low.
No bias now and yet there was before. Only the cap has changed, we have Qe9 and 11 refitted as before.
Try it with a speaker... without a scope its as good a clue as any as to what may be going on. Keep the volume low.
No bias now and yet there was before. Only the cap has changed, we have Qe9 and 11 refitted as before.
yes, and in to the bias pot, we get 8.18v. leaving bias pot, set at 1K there is 7.18. same to R27. leaves R27 7.2v bur before it can get to the .047 ohm there is no voltage.
Something seriously amiss with those readings. No open circuit print ? Each driver and output transistor should have approximately 0.7 volts across the base emitter junction.
So you are losing 8 volts between Re27 and the output. That should be easy to find. Just stick your meter lead on the speaker positive output and work back.
The offset itself is still at around 0.2 I take it ?
So you are losing 8 volts between Re27 and the output. That should be easy to find. Just stick your meter lead on the speaker positive output and work back.
The offset itself is still at around 0.2 I take it ?
low volume. sound good. reception aint great here, but L sounds as good as R here now. when i smoked the last 5401 (or was it the 5551?), i had the same results. sounded good, until i cranked it.
afraid to turn it up 🙂
afraid to turn it up 🙂
Don't turn it up with the bulb fitted.
So its basically working. I have serious doubts over Qe9 and 11. If they are leaky then will cause a problem. Did you test them when you took them out ? I really think they should come out and be tested (or left out for now). If they are difficult to get too then just snip the emitter lead of both to isolate them.
So its basically working. I have serious doubts over Qe9 and 11. If they are leaky then will cause a problem. Did you test them when you took them out ? I really think they should come out and be tested (or left out for now). If they are difficult to get too then just snip the emitter lead of both to isolate them.
offset at speaker terminals .186.
in from speaker, at Re49, same .186
between Re49 and Ce25 rises to .191volts. BUT on other side of Ce25, 0volts?
is this significant? take a peek at the schem. where/why does the voltage rise on the Ce25 side of Re49?
in from speaker, at Re49, same .186
between Re49 and Ce25 rises to .191volts. BUT on other side of Ce25, 0volts?
is this significant? take a peek at the schem. where/why does the voltage rise on the Ce25 side of Re49?
I am sorry to say that amplifier repair is about procedure
I wouldn't connect a load to an amplifier that presents 200 mv offset ...
I wonder why don't you spend some time tracing the fault ...
i wouldn't also connect a load to an amplifier before i scope for signs of oscillation ( after the modifications made of that level done )
Kind regards
Sakis
I wouldn't connect a load to an amplifier that presents 200 mv offset ...
I wonder why don't you spend some time tracing the fault ...
i wouldn't also connect a load to an amplifier before i scope for signs of oscillation ( after the modifications made of that level done )
Kind regards
Sakis
One end of Ce25 goes to ground and so will have zero volts. The other end will just reflect the offset.
Listen 🙂 You have around 0.2 volts offset as measured from ground to Re49.
Now move back one step and measure the voltage on the base of Qe21. It can not be higher than around 0.9 (your offset plus 0.7). If that's good then move back another step to the base of Qe17. Whatcha got. If you have 20 odd volts on Re19/Re27 junction you must now be seeing that on Qe17 base.
I know 🙂
you have a last resort :
Check shipping cost to Athens ...
Snail mail will probably be cheap .....😛
Check shipping cost to Athens ...
Snail mail will probably be cheap .....😛
ok then. well thank you so much for the help guys. appreciate it very much. i will let you know how i make out.
best,
aidan
best,
aidan
I actually mean this ... i will be happy to repair your amp for free you never know shipping might be low cost
In this way we all might gain something you an amplifier and the others a drop in replacement of parts for the specific model ...
Other than that clear your head from all this quick posting , use the methods given by me and Mooly to trace the difference in the operation .... use the scopes to see for signs of instability ...
Kind regards
Sakis
In this way we all might gain something you an amplifier and the others a drop in replacement of parts for the specific model ...
Other than that clear your head from all this quick posting , use the methods given by me and Mooly to trace the difference in the operation .... use the scopes to see for signs of instability ...
Kind regards
Sakis
And I just wish I had it in front of me to see what was going on with it.
(One thing that would make sense to myself and Sakis I'm sure would be for you to write on the circuit the voltages that you actually have)
(One thing that would make sense to myself and Sakis I'm sure would be for you to write on the circuit the voltages that you actually have)
you may as well remove parts from the amplifier to make less shipping cost transformer for example top cover and so on
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