I'm just re-reading what I wrote and its wrong... sorry about that. The base of TR9 or TR10 link to the diodes.
All you are doing is removing the preset and linking two of the empty pads together. The two you link must electrically connect the collector of TR5 or TR6 to the diodes.
The little diagram is correct.
Sorry about that.
All you are doing is removing the preset and linking two of the empty pads together. The two you link must electrically connect the collector of TR5 or TR6 to the diodes.
The little diagram is correct.
Sorry about that.
1 step forward and....... the wire which I have terminated to the base of TR5 just made contact with the chassis. Saw a little spark. Is this bad news??
Yes, that's bad news Let me just think what that will have done.
That's a relief 
If you have a new transistor available then it might be worth replacing it anyway... depends how much charge it dumped as to whether it might be impaired or suffer reliability issues. It is probably fine but...... if it was mine I would replace it.
So the trim pot is now linked out.
Have you still got the original link in place between the two base's of the drivers?
With new diodes fitted that original link is to be removed leaving just the preset shorted.
Electrically it must be as that little diagram a few posts back.
If you have a new transistor available then it might be worth replacing it anyway... depends how much charge it dumped as to whether it might be impaired or suffer reliability issues. It is probably fine but...... if it was mine I would replace it. So the trim pot is now linked out.
Have you still got the original link in place between the two base's of the drivers?
With new diodes fitted that original link is to be removed leaving just the preset shorted.
Electrically it must be as that little diagram a few posts back.
That sounds promising.
You can now very (very very) carefully just check that there is approximately 1.8 to 2.4 (ish) volts across that chain of diodes.
In other words you are measuring the voltage between the the driver transistor base's but its much safer just to measure across the diode chain. Each diode should have around 0.65v across it and all three add up to give the total.
If you listen to the amp now then you might find it sounds a little better at low volume, at least on that channel. Also always just confirm there is no DC at the speaker output after doing any work. That's good practice whenever anything is changed or altered.
If its all good then we do the same on the other channel.
Feeding time after all that excitement I think
You can now very (very very) carefully just check that there is approximately 1.8 to 2.4 (ish) volts across that chain of diodes.
In other words you are measuring the voltage between the the driver transistor base's but its much safer just to measure across the diode chain. Each diode should have around 0.65v across it and all three add up to give the total.
If you listen to the amp now then you might find it sounds a little better at low volume, at least on that channel. Also always just confirm there is no DC at the speaker output after doing any work. That's good practice whenever anything is changed or altered.
If its all good then we do the same on the other channel.
Feeding time after all that excitement I think
Perfick
That is probably as far as it can be taken without the pre-sets. All you can do now is just carefully look it all over and perhaps replace that TR5 that took a bit of a hit.
As before, if you do replace it then just check the DC offset at the speaker terminal is zero before connecting speakers.
If you are happy is all good then it can be tried on full mains now and just used as normal. Initially just keep a check that the output stage isn't getting hot (unless playing loud).
That is probably as far as it can be taken without the pre-sets. All you can do now is just carefully look it all over and perhaps replace that TR5 that took a bit of a hit.
As before, if you do replace it then just check the DC offset at the speaker terminal is zero before connecting speakers.
If you are happy is all good then it can be tried on full mains now and just used as normal. Initially just keep a check that the output stage isn't getting hot (unless playing loud).
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