What would you do with the parts from failed build?

[ToneJunkie]

So here is a JTM 45 that I built in a Stout Chassis.  I did this several years ago and it has always hummed way to much.  When I was building it I was warned about how close the transformers were but I went for it any way.  Here are the pictures and my questions is below those. 








I was wondering what you do when a build does not work out?  Do you just gut it?  I actually don't have any desire to build another amp... Oh Well.


P.S.  My main amp for years has been a SLUCKY AB763 Lite and I have played over 100 gigs in the last 3 years and its my favorite!

[glass54]

Nice work ToneJunkie  .
Can you isolate the hum, ie power amp vs Preamp? Maybe silly questions but could it be improved with extra filtering of screen supply?
(You did say that you had no further desire to do more to it)
In regards to AB763 Lite, does that mean Sluckey wins again? 
Kind regards
Mirek

[Latole]

I don't know it it is the issue, I see some wiring issue. I'll do a better wiring dress.

[tubenit]

I'd try this first.

- Use 12AY7 in V1 , 12AY7 in V2 and then a 12AT7 for the LTPI
- Use smoothing caps plate to cathode on V2a
- Use enhance cap across plate resistor going into the LTPI
- Not use any cathode caps on V1 higher than 5uf and no cathode cap on V2
- Change the amp to cathode biased
- Use shielded wiring on anything where you're going near heater wires or high voltage wires or long runs
- I might construct an aluminum shield to mount on the chassis between the preamp tubes and the transformer next to it.

Those are all pretty easy to do and quick experiments.  IF that doesn't significantly lower the hum,  I'd remove all the components (board, pots, trannies, etc....)   and rebuild it in a larger chassis

[DummyLoad]

strip it and move all those components into a 17" wide or larger chassis. follow the marshall layout, but don't place the grid stoppers from the input jacks to the first stages on the board like marshall and fender did on the 5F6A bassman - use the later fender plan like on the deluxe reverb.

i'm kind of partial to this one.     punch your own PT, OT & choke holes. 

--pete

[shooter]

+1

when you strip it, consider moving the heater wires, either in line with tubes, or the "other side" of chassis

[Latole]

strip it and move all those components into a 17" wide or larger chassis. 

--pete

Do you really think he will follow your ( very good ) advice ?

[Latole]

+1

when you strip it, consider moving the heater wires, either in line with tubes, or the "other side" of chassis

+1

Like my first answer ; wire dress could be the issue

[sluckey]

strip it and move all those components into a 17" wide or larger chassis. 

--pete

Do you really think he will follow your ( very good ) advice ?

Are you really trying to be helpful? If so, you're doing a piss poor job!

[Latole]

Are you really trying to be helpful? If so, you're doing a piss poor job!

[/quote]


I do not share your opinion at all.
Give as a suggestion to rebuild the amplifier in a new larger chassis when it is obvious that the author of the subject will not do it.

Better to try to make the amp work well with the existing chassis. This is possible by retouching the wiring for example.

ToneJunkie do you agree with me?

[ToneJunkie]

Nice work Tone Junkie 

Thanks I will try and look at your fix suggestions!

I'd try this first.

- Use 12AY7 in V1 , 12AY7 in V2 and then a 12AT7 for the LTPI
- Use smoothing caps plate to cathode on V2a
- Use enhance cap across plate resistor going into the LTPI
- Not use any cathode caps on V1 higher than 5uf and no cathode cap on V2
- Change the amp to cathode biased
- Use shielded wiring on anything where you're going near heater wires or high voltage wires or long runs
- I might construct an aluminum shield to mount on the chassis between the preamp tubes and the transformer next to it.

Those are all pretty easy to do and quick experiments.  IF that doesn't significantly lower the hum,  I'd remove all the components (board, pots, trannies, etc....)   and rebuild it in a larger chassis

I will try those!

strip it and move all those components into a 17" wide or larger chassis. follow the marshall layout, but don't place the grid stoppers from the input jacks to the first stages on the board like marshall and fender did on the 5F6A bassman - use the later fender plan like on the deluxe reverb.

i'm kind or partial to this one.     punch your own PT, OT & choke holes. 

--pete

Yeah I don't really want to put the time in but it looks like that may be on the horizon :-)

[ToneJunkie]

OK now that I really look at what is ahead of me... I have 3 amps that I have built that I want to fix.  I have always been a "paint by the numbers" kind of amp builder with little understanding of troubleshooting so this is going to be my chance to learn a bunch about my previous mistakes and how to troubleshoot.  The other two amps I have to fix I believe will be much easier fixes. So... This one goes back on the shelf and I will come back to all your suggestions after I fix (with everyone help of which I am very grateful for) the other amps...  Here we go! 

[Bieworm]

I buy total blank chassis' for 12€. Starting from scratch gives me more pleasure. Did that on my last 2 builds.. noisewise they're both fine (except for the oscillation I can't seem to find, but still have a better sounding amp with all the tweaks I did during the quest for the osc. LPT instead of paraphase. Smoothing caps, higher value coupling caps that got rid of some nasal sounds.

[sluckey]

Are you really trying to be helpful? If so, you're doing a piss poor job!

I do not share your opinion at all.

Yes, of course you would think that!

[kagliostro]

Have you tried using shields between irons (PT - OT - Choke) and irons and tubes ?

Franco

[glass54]

I had a second look ToneJunkie. All the other responses got me excited esp when I noticed your (secret) heater wiring  .
I realised that while the project is almost gorgeous to look at, your lack of heater space may have undone you.
+1 with DummyLoad and Shooter. (I am really looking forward to seeing a very successful rebuild  )
Kind regards
Mirek

[dwinstonwood]

That is a cool amp. I want to build a KT66 amp myself (I assume that's what you're using). I think that '67 Winterland Cream show is all about boiling/melting KT66's, but I could be wrong - listen to Sleepy Time Time for some crazy, choking compression and sag.

Anyway, I recently built a high(er) gain AA864 in that chassis and it is totally possible to to have a no hum amp in that small space (all thanks to sluckey).

I'm new to amp building. But, after filtering is set right (component choice), I really think noise comes down to wire length and routing; component location; and grounding points.

[ac427v]

Beautiful amp. It should not be sitting on your shelf!The only wiring issue I see is the heaters to V1 are too close to the input jack and grid stoppers. You could remove your nicely twisted heaters to V1 but leave the other tube heaters intact. Then run straight (untwisted) wires from V2 to V1 like Soldano does. That would move the heater AC away from the input jack, wiring and resistors. It would mess with your consistent pattern of heater wiring but when the amp is closed up and roaring you'll forget all about that.

[glass54]

+1 ac427v.
I think the Soldano idea is worth exploring. Maybe do the Heaters overhead for V1 to V3, shorten V3 to V4 with twisted pair, redo short twisted pair to V5 and feed V5 directly from Power Tx. Fit new lower current wire, tightly twisted pair to lamp. (not sure if you use CT on heaters or pair of 100R as we don't have a schematic). This method would save a Chassis transfer  .
You could consider some shielded cables from Turret board to pots (only in critical spots) and maybe a a Switchcraft 12A input jack??
This amp is too nice (gorgeous  ) to be sitting on your shelf.
We all know what your new years project will be
Kind Regards
Mirek

[sluckey]

If you decide to redo stuff in that same chassis, take a look a Hoffman's Plexi6V6 page. Probably a lot of ideas that will apply to your amp. Things such as filament string...

     https://el34world.com/projects/Plexi6V6.htm

[Glenn]

Your build looks great.
I would start easy and just turn your input jack so the lugs face the volume pot, and the reroute the 68k resistors away from the heaters....
Might be enough
Don’t give up.