#124 started

[erwin_ve]

Happy birthday Marcus!
Hopefully your built will soon be roaring.
Since there is NO voltage on your v1 and v2 cathode I also suspect the connection at the tube pins.
Did you bent them? I once bent them too much and they broke. Was a pita to find out.

[Sven]

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[erwin_ve]

Thanks. I did not know about that archive - excellent info! This schematic from this (newly discovered today for me) archive is different from what I had, and better... Yes, that's it.

That schematic is post 84(skyliner tonestack!) and was drawn and posted here at ampgarage by member odourboy. It was taken from the info that was posted by member Ayan, way before there was a beautiful files section.

[Sven]

NOW COULD SOMEONE CLARIFY, could someone give the right answer to my very clear question. Thanks.

[erwin_ve]

NOW COULD SOMEONE CLARIFY, could someone give the right answer to my very clear question. Thanks.

Sven: the pre 84 has 250k bass pot etc
The post 84 has 500k bass pot etc. The post 84 schematic is the #124 schematic as it was posted here by Ayan. All the pics you see in the dumblearchive link for 124 are the post 84 schematic with 500 k basspot.
Round mid eighties earlier dumble amps got updates by HAD with the specs for 500k basspot(skyliner tonestack) and some other things. Many members here like the old specs so Tony provided Both schematics! How cool is that?

One note: when editing your previous post seems like someone was unwilling to answer your questions. It made a agressive impression on me. Peace.

[Sven]

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[norburybrook]

Sven. There's no confusion. I'm building the#124 low plate classic. There's a clear layout and schematic posted in the files section.


@martin, what do you mean by a resistance being ~Rk?

I'm home tomorrow so will measure my cathode resistances to ground

Marcus

[martin manning]

@martin, what do you mean by a resistance being ~Rk?

Measuring resistance from a V1 or V2 cathode pin to ground you should get something like the cathode resistor value (even though it's paralleled with a cap).

[Sven]

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[ToneMerc]

Let us look at the DUMBLE FILES with pre-skyline schematics on the first item of the first thread dedicated to D 124 model.


1. There is Treble potentiometer with ¨250k Alpha¨ written on the scheme. No indication whether it is logarithmic or linear. Alpha is a brand of pots.

2. Further, there is Middle pot with 100k written in parenthesis. No indication whether it is logarithmic or linear.

3. There is a Bass pot with 250k written in parenthesis. No indication whether it is logarithmic or linear.

4. There is Volume pot with 1MA written – first indication, obviously, logarithmic pot.

5. Same as 4., there is Master volume pot with 1MA written – obviously, logarithmic pot.

6. OD trim has only 100k written in parenthesis – no indication whether it is logarithmic or linear.

7. Level pot has 100kA, obviously, logarithmic.

8. Ratio pot has 100kB, obviously, linear.


Thus it is obvious that four out of eight pots have NO indication in the schematics whether they are logarithmic or linear. Layout is for SKYLINE model, thus it is not for the pre-skyline model of 124 - thus, clarification is needed, no doubt about it. ! http://ampgarage.com/forum/viewtopic.php?t=5719

Sven, this is a Marcus 124 build thread and he stated that there is no confusion on his part concerning his own build. So for a fleeting moment try to remind yourself that this is his build thread, not yours.

Thus, as a common courtesy why don't you stop trolling and robbing this thread and at least allow him an opportunity to get the bugs worked out his build.

Sorry, but you are still the only one confused. Even Marcus has told you more than once, everything you need, including layout for a 124 classic is on the Files section.

TM

[erwin_ve]

Marcus: between groundingpoints at input and Pt: is there continuity ?

[amplifiednation]

As suggested, I bet there is something wrong with your heater wiring for the preamp. Sometimes getting the solder to flow on those two-wire connections can take a little but more solder and heat. You might have continuity because the wires are connected, but there is no connection to the tube pin.

Can you post a pic of the preamp tubes? Did you measure heater voltage? Pins 4 and 5 are connected?

[amplifiednation]

Also your PI voltages - are the cathodes tied together? You jumpered pin 3 and 8? Check those solder joints too. That can also be a tricky connection without extra attention.

[norburybrook]

hello people.


got home today and managed to get a few minutes with the amp.

cathode resistances were as they should be.
I pulled the valves and re checked for continuity, this time I found a poor connection between one side of V3 and V4 so removed the wiring and re did it.

I fired up and now had around 176vDC and 1.5v on the plates and cathodes of V1 however I've now got a terrible hum.

progress though none the less.

the OD and pre amp boost are not working , well the OD switches but I loose sound, it's there but very faint.

the 3 switches work fine, the tone controls work fine.

the master volume is scratchy/noisy and the presence control seems strange in that it doesn't seem to do anything then between 7 and 9 changes the sound quite dramatically the goes back to doing noting at 10.


these are just my quick experiences from 15 mins of fiddling today, sorry they're not very technical!!!!.

I'll be able to spend the day on this tomorrow so any ideas to try for the morning would be welcome.

thanks again


Marcus

[martin manning]

So it was a heater string power issue with V1 then? That would square with 0V on the cathodes. Why not measure and post a complete set of voltages for tube pins and power supply nodes?