Questions about "Final ODS-101 Schematics" post

[ic-racer]

Do you happen to have the link for #124? I cant seem to find it.

Do you mean the pictures or schematic? I don't remember where on this board I got the schematic, its just easier to re-post it in this thread if that is OK with the forum rules.

[odourboy]

Do you know the source of that schematic? There seem to be a few discrepencies in values between it and what Billy/Gil posted about 124.

In particlar:
1) The bass pot value
2) The OD entrance trimmer value
3) The drive pot value

[ryanf]

Thanks! I was looking for the schematic, but the image isnt showing up for me when enlarged.

[Structo]

yes the schem isn't coming up.

[odourboy]

I had the problem too. Copy it to your machine then open it - that worked for me.

[ic-racer]

As you can see, or already know that schematic dates from 10/11/06 and I have searched most of the comments by the experts on the schematic. Too bad these comments are scattered throughout this board.

The notes I have on the 124 rev 2 schematic are as follows:

1)OD trimmer was possibly modified by Mr D on the original so that it was around 300 K. It started life as a 500k as marked on its body. So the 100k shown in the schematic is not exact.

2)The take off for the bias supply looks like it eminates from the plate voltage, but in reality there will be a 60V tap on the Fender transformer.

3) the indicated "OD Level" pot may have been 250K

4) the hand written notes with the #124 pictures show the filament supply to be: a.) Not grounded at the 'center tap' and b.) connected to ground on either side with 100K resistors. My searches on this topic indicate that either way is OK for reducing hum.

5) not shown (but discussed on the boards) are the voltages which are 440V at B1 and 190V at B5

6) the presence or lack of the FET circuit may influence the lower B voltages.

One thing I was thinking of doing is to update the 124 schematic to include the 50/100 and the FET and possibly the relays for the sake of 'historical completeness'

[Structo]

Did you see this thread?
There is a link there with a lot of Dumble info.
Particularly #124.
There is a zip file at the top of the #124 link that you can download with heaps of photo's and hand drawn schematics.
https://tubeamparchive.com/viewtopic.php?p=39851#39851

[odourboy]

As you can see, or already know that schematic dates from 10/11/06 and I have searched most of the comments by the experts on the schematic. Too bad these comments are scattered throughout this board.

The notes I have on the 124 rev 2 schematic are as follows:

1)OD trimmer was possibly modified by Mr D on the original so that it was around 300 K. It started life as a 500k as marked on its body. So the 100k shown in the schematic is not exact.

2)The take off for the bias supply looks like it eminates from the plate voltage, but in reality there will be a 60V tap on the Fender transformer.

3) the indicated "OD Level" pot may have been 250K

4) the hand written notes with the #124 pictures show the filament supply to be: a.) Not grounded at the 'center tap' and b.) connected to ground on either side with 100K resistors. My searches on this topic indicate that either way is OK for reducing hum.

5) not shown (but discussed on the boards) are the voltages which are 440V at B1 and 190V at B5

6) the presence or lack of the FET circuit may influence the lower B voltages.

One thing I was thinking of doing is to update the 124 schematic to include the 50/100 and the FET and possibly the relays for the sake of 'historical completeness'

124 definitely had a FET circuit which will for sure affect the B+ voltages - so depending on what you wish to achieve with the schematic, either the FET circuit or a (150K) FET 'simulation' resistor should be included. The schematic indcates the bass pot is 250KA - it should be 500KA. All indications are that the drive pot is indeed a 250KA. (Billy's notes, Gil remarks and the photos.) The 190V on B5 I'm pretty sure should be a V1 plate voltage. B5 'has' to be 300V range.

Like I said, I'm not sure what you want to achieve with the schematic, but if it is labeled as #124, then IMHO it should be true to 124. If it's for your own build - that's cool, but then call it something else.

[ic-racer]

Like I said, I'm not sure what you want to achieve with the schematic, but if it is labeled as #124, then IMHO it should be true to 124.

It would be nice to have the #124 schematic as close to original as possible, as a reference, and the 101 schematic for 'builds' etc. I didn't have anything to do with the creation of either schematic, I was just contemplating picking up where the other guy left off (this is a 'community project' right?), but I may not be the best one for the job I don't have any schematic creation software. One thing I COULD do is to just add a text 'comments' section to the bottom part of the schematic and then just throw it up on the board for a critique.