relaise swiching on ODS 124

[hans-jörg]

Hi,
yes, it is on ground. Via return Jack to output jack than chassis. Could be a bad connection. But then this must cause more problems.
But it is the aerea.
I use cliffs (or neutric) jacks, so I have to ground them. The swichcrafts are direct grounded.
This could be the problem, that my grounding is too long (goes to Gound 2) and on wron place.

Thanks and Regards

Hans-Jörg

[Structo]

If you follow the ground scheme on #124 you should have zero problems.

Note there are 5 points and it is very specific what goes to each point.

[hans-jörg]

I will bolt the ground pins of send/return right byside of the jacks to ground. This should help. Or better - I mount 2 swichcrafts

Thank you

Hans-Jörg

[hans-jörg]

Hi Gents,
I changed to swichcraft. Grounding goes direct through Jacks. But ..nothing changed. at least a bit MORE hiss.
My next try is Master direct to PI without In/Out. Let´s see what happens.
Could it be I changed the places of In/out and speakers out (I rearly dont know why) - so my In/out is very close to first Poweramp tube.

Thanks
Hans-Jörg

PS this picture is with the previous jacks. But you see the position - I hope.

BTW whatfore is the 220k/250pF between In and Out? Other layout dont have it. (low plate classic, f.e.)

[hans-jörg]

Ups, I think I found it. But only theoretical because I´m not at home - but I´m wathing the whole time the layout
I think I forgot the connection between the 390 ohm resistor and the 4k7. Therefor the hiss decrease when I touch the grid of V3a (pin 2) with my DMF wich was grounded on the other side. I´m 99,99 % shure that I produce this bullsh....
I´ll verify it in the evening.

By, by, I´m sorry for posting so much because of such a ......

Hans-Jörg

Ok, the good thing is - I´ve now swichcrafts

[Structo]

I hope that is it.

You also have a very crowded chassis which will make lead dress even more critical.

Good luck.

[hans-jörg]

"crowded" - you said it rearly nice. But beleave me, I know every single wire - because I had 3 or 4 times in my hand at least. So , at the ende, my planned layout is away. But I have to say that the PowerAmp Section is absolutly quiet. No Nois, no hum at all.
I allways promise to me: when I finished it I´ll start with cosmetics.
Ok, I´ll let you know if I was right with my failure.

Thanks in the meantime

Hans-Jörg

[hans-jörg]

Hi,
I dont know further. The connection I wrote above was there. I took the wire from Master wiper direct to PI (so no in/out). no difference. I sodered all connections around the V3 new. nothing. The qualaty of the hiss ist still the same. No moving of wires reflects to it. Sometimes I think to hear a kind of swinging when OD is on. As stronger the OD as stroner the swinging. Could I try to swap the connction OT secondary, or on the PI?
It is still so that the hiss decreases when I touch the grid ov V3 (Pin 2) with DMF.
I become mad of this hiss.

Hans-Jörg

[hans-jörg]

Hi,
ok, I have an other guess:
I dindn´t shielded the connections to my OD Pot which is on the back pannel. These connection are crossing the heater supply and so on.
This could be the point.
Lets see tonight.

Hans-Jörg

[angelodp]

For sure change that OD ( drive pot - wiper ) to shielded. Only ground one end.

[hans-jörg]

Noop,
I changed to a trimmer to see the difference. Nothing!
It´s still humming. BTW that should be clear, because the hum/hiss is not on 1st and 2nd stage only on V3 - PI.
So I guess I have to swap the secondarys from OT. Best on the coupling caps because the OT wires are different long now. I think thats the same, or?

Hans-Jörg

[hans-jörg]

Hi Gents, its me again with still the same problem.

Is it normal that the signal of the whole amp is death when the relay is raised (I mean even the non OD channel)? I have the OD relay exactly wired like layout above.
And:
I found out, that the ground wire from relay reflects nothing if its disconnected or connected with ground (I had it on the bus and wanted to change to ground point 1.

BTW: when relay is in everything works normal, only the hum which increases when Master turns louder.

Greatings

Hans-Jörg

Edit:
as long as I can read the schema about 124 I´ve to say that evan the OD relay is wrong shown in the layout. What is the middle point of rel. swich: the grounding (no) or the line from trimmer+220k ? (yes)
In the layout its opposite and diffrent then the schemata 1988!

[Dr d]

Tony, if you are out there!!!!!! I'm a little confused why the back panel PAB switch (#124/102) has no connection to ground. Otherwise, how is the relay activated? Cheers, Doc.

[martin manning]

Tony, if you are out there!!!!!! I'm a little confused why the back panel PAB switch (#124/102) has no connection to ground. Otherwise, how is the relay activated? Cheers, Doc.

A three-position R/J switch (on-off-on) makes PAB accessible from the front panel with the R/J in the middle (off) position, and several Dumbles are known to have this feature. See discussion here: https://tubeamparchive.com/viewtopic.ph ... 924#133924

[Dr d]

Martin, thank you. Kind of makes the rear panel switch redundant. I shall add a ground to it and have use of both methods. Cheers.