Jim Lesurf wrote:



if this is intermittent, then I'd suspect that there is an unreliable power
or reference level connection. Possibly to the board at the front of the
set that holds the switches, etc.
Thanx,
I'll check this....

The actual signal switching is done using 4066 CMOS switches (at least in
issues 1 - 3 of the amp). However some other logic is used to control this
and (when working correctly) ensure only one non-tape input can be selected
at any time. That would probably be the failure point as the LEDs are also
driven from this. The transistors here are simply to give enough boot to
light the LEDs, I think.
Thanx for the reply,
I tested the transistors and they seem ok, and yes I think they are
drivers for the leds. I will next replace the 4066, as I see thats next
in line. As for "some other logic" controlling the inputs, I am at a
loss here......

If no-one else has a diagram to hand, ask again and I'll see if I can
produce a scan. Do you know what issue of board you have? (Or can say the
serial number.)
Thanx, a schematic would be great. I found a 44 schematic on the web,
and trying to cross reference that to get an idea as how this thing
works, but it's a pain....I dont even know how similar they are...

I can tell you the serial number tomorrow...

thanx again..

regards,
nicolas


BTW, does this thing sound ok? I am a bit put off by all the tl071
opamps that populate this thing. Aby recommended mods?


I find the 071's work fine and would not personally change them.
Replacement with a different IC might lead to other problems. However I do
change some other components to alter the action of the 'tone controls' a
little. You can also easily change which input is selected by default by
moving a capacitor. :-)

Slainte,

Jim