New ODS 100W build with pictures...

[Bob-I]

I am assuming that Hammond, by copying the same color wires as the original Twin transformer, has also copied the same internal hookup.

Assume nothing about these colors. My power up routine includes leaving the NFB wire disconnected, then once I get sound, I briefly touch it to the contact while holding my ears.

[ic-racer]

Frustrated

All Fender Twin schematics and all Dumble clone schematics I have all show this same schematic drawing convention:

TOP half of PI tube gets preamp input which feeds TOP half of of the power tubes which are connected to the TOP primary lead of the output transformer and then the TOP secondary lead is connected to NFB and the tip of the speaker jack.


When I plug my Hammond schematic (that came on a piece of paper in the box with the transformer) into my schematic with the #124 colors in place it comes out upside down! (ie the BOTTOM OT secondary is the green one that goes to the NFB and to the speaker jack tip.)

So one or more of the following is true:

1) The Hammond schematic is different from the original Fender transformer (ie wires are same color but connected different inside the transformer)

2) It still might work 'upside down' like this...

3) I made an error following the colored wires in the #124 pictures.

EDIT POST***************************************************
I made an error following the pictures. I DID get the brown and blue reversed coming out of the PI. I'll need to update the schematic again......

[ic-racer]

After a breif hiatus fixing the power supply in an 8x10 enlarger ( http://www.largeformatphotography.info/ ... stcount=44 ) and changing the belt in my vintage 3 3/4ips BIC tape deck ( http://www.audiokarma.org/forums/showth ... p?t=146577 ) I can get back to this project.

I have been 'thinking tube' too long, the first 2 hours I spend working on the integrated circuit board on that power supply, I got a lot of strange readings. I was measuring voltage relative to a chassis ground. Duh..that power supply is designed to ISOLATE the circuit board from the chassis...

Anyway, back to tubes. I was just informed my parts will be here in the next few days!!!!

I went back and forth with having Niki at Ceriatone make me boards with the exact components as #124. However, it seemed just getting the OD input stage would be a problem (ie the 350k trimmer). And I though this might just be the 'tip of the iceburg' in terms of component matching. Because, we don't really know the measured values of #124's other components.

What I DO KNOW is that the clips of Niki's amp on the Ceriatone forum sound very good to me. So, since I didn't think I could make an exact electrical reproduction of #124's board, I decided to go with something that is very close to #124 and is known to sound good.

I'm a little time-limited on this project also, so getting pre-made boards form Niki seemed like the way to go. We will see....

[Funkalicousgroove]

I have 350K trimmers, do you need one?

[ic-racer]

I have 350K trimmers, do you need one?

Yes I would. It would be nice to have some components on hand for the potential tewaks to come. In fact 4 of the #8-32 weld nuts would be great also. How much & can I paypal?

[ic-racer]

Boy, this is the slowest build...we are traveling at a 'break-neck' speed of approximatly one component per month.

This month's component is the FET input jack.

I could not tell the exact type of jack on #124. The jack schematic required to make it all work the way it is supposed to does not seem to fit any of the Switchcraft brand jacks. At the suggestion of others, I am using a stereo jack, just so I have two switches inside. This one from Kobiconn looked like it would work.

http://www.mouser.com/catalog/specsheets/KC-301065.pdf

[ic-racer]

This is just a bunch of input jacks. In all the pictures it looks like the FET and NOR inputs use different jacks from different manufacturers. If I believe this than I can sleep better, knowing that I couldn't find an appropriate FET jack in the Switchcraft catalog.

[ayan]

This is just a bunch of input jacks. In all the pictures it looks like the FET and NOR inputs use different jacks from different manufacturers. If I believe this than I can sleep better, knowing that I couldn't find an appropriate FET jack in the Switchcraft catalog.

The input jack is a Switchraft isolated break type. The P/N is 502-13E from Mouser for the metal bushing one, but Dumble used the nylon bushing type so he could isolate the ground from the chassis, and that P/N is 502-113E. The nylon version has a lead time of 6 days and is a bit cheaper than the metal bushing one. I clarify that Dumble uses an isolation washer on the NOR input and long bushing Switchcraft jacks, which are the L12A. For what it's worth, I use metal types on both, not isolated fromthe chassis and never had a noise problem in my amps.

Gil

[heisthl]

A Rean stereo jack will do this too and give you the isolation. You can put one in both places if you want them to match.

[ic-racer]

The input jack is a Switchraft isolated break type. The P/N is 502-13E from Mouser for the metal bushing one, but Dumble used the nylon bushing type so he could isolate the ground from the chassis, and that P/N is 502-113E. The nylon version has a lead time of 6 days and is a bit cheaper than the metal bushing one. I clarify that Dumble uses an isolation washer on the NOR input and long bushing Switchcraft jacks, which are the L12A. For what it's worth, I use metal types on both, not isolated fromthe chassis and never had a noise problem in my amps.

Gil

I looked at those jacks and passed them up because I could not figure out how to wire it. Maybe the schematic I am using is not correct. I'm perplexed. The pieces in the picture below just don't seem to add up and I don't know why

The other thing I am perplexed about it the isolation of the jacks. From what I can tell, I see no other ground wire to the jacks; looks like both jacks need to be grounded the the chassis. To me it looks like the chassis by the NON-FET jack has been scrapped and there are 1 or 2 star washers to 'dig-in' to the chassis and provide ground.

On the FET input it looks like he has a jumper from the neck ground pin to the rest of the pins that need ground. Implying to me the neck of the jack is grounded to chassis.

What do you think?

[ic-racer]

This is what I cobbled together...mostly based on looking at the pictures, so I'm not certain how close it is.

[heisthl]

Another picture, another thousand words.....

[ic-racer]

Another picture, another thousand words.....

Excellent, thanks for posting this.

[BobW]

Since I didn't want to wait for backordered parts on my 100W Funk chassis build, am waiting for 99% of the parts to arrive from Mouser (Rs and Cs, etc), Magic Parts (Rs and Cs, etc), CE Distribution (Caps), etc, Weber (OT, etc), and Mojo (PT). I'll post my progress on a new post.

[ic-racer]

Seems like all the Dumble pictures I have seen show a handle strap with 4 screws. The closest I could find was this Fender strap which I think I will use.