#102 Started. Checking in

[amplifiednation]

I have made some good progress the past week or so.

I have the power board all wired up, bias board, cleaned up the pot wiring (rerouted some of the wires to run along the inside edge of the chassis.

if you notice a slight increase in mini cable tie stock today, it was because of this build. i must have had the relay runs tied four times when each time i realized there was more wires going back there!

all i have left is the standby switch, the input and fet jack, a continuity check and once over, and I think i'm about ready for the smoke test!!!

Anyone try these TAD filter caps? They are nice and small! The power section sure does get busy...I paid attention to every wire and every connection. I wish I could clean it up a little bit.

And yes, I burnt the sh*t out of the PAB relay. It should still work, I'll get another one ordered up for aesthetics. What a disappointment that was.

[dcribbs1412]

Nice work Taylor
Haven't used the TAD caps...not sure how much it matters but
the PPS I did has 2 350V 47uf caps at C3 C4...they are a little bigger
than the 250V caps...

Darin

[amplifiednation]

Thanks Darin.

This is all done!

I'm gonna power it up tomorrow after I'm done with cabinets. I hid bunch of leads under the boards. It cleaned it up a lot, I hope there isn't any crosstalk. It's not easy with this much wire to put it all in good spots. This was my first Dumble build...hoping for good things tomorrow.

The more I look at the power section I think I can clean it up a little bit, maybe have the choke and OT leads connect from under the board. We'll see what happens with the power up. I also have a Bassman 100 OT I might swap in. I have a Twin in there now.

If anyone has any last words...speak now! I've got a limiter I'll be using and follow the regular start up procedures.

...and i finally changed the input resistor.

[Guitarman18]

Great looking build Taylor,

I was just wondering where you have grounded you Presence cap. Often it is grounded at the Power amp return jack, but not always. I'm hoping I just can't see it.

Good luck!

Cheers,

Paul.

[amplifiednation]

Great looking build Taylor,

I was just wondering where you have grounded you Presence cap. Often it is grounded at the Power amp return jack, but not always. I'm hoping I just can't see it.

Good luck!

Cheers,

Paul.

Yup looks like I missed that connection!

Thanks for checking my work.

[ToneMerc]

Great work Grasshopper

TM

[amplifiednation]

Powered up. The amp is passing signal but does not sound good!

I may have overheated the overdrive pots...they don't seem to be functioning well.

Sound cuts out without overdrive engaged...PAB seems to be working.

Using 1973 twin OT, 1970 twin PT

Mains 122
Sec 676

B1/B2 451
B3 433
B4 327
B5 320

v1a 199
v1b 207

v2a 195
v2b 195

v3 290

plates 443

I set the bias to 32 just while i try to test.

What are the signs of overheated pots? I should have some to sub out.

Also I'm not sure on the PAB relay wiring. I have a feeling thats where my problem might be...

[martin manning]

Hi Taylor, your voltages look reasonable, but I expect V1 plates to be ~10V lower than V2. Could be just the tubes you have in it. Overheated pots will cause loss of signal. That's the OD relay you're showing in the center of the photo... I think you need to wire it like this drawing. You have the contact sets switched relative to mine so I adjusted the drawing below to be close to what you have.

[amplifiednation]

Hi Taylor, your voltages look pretty good for now, so your power supply and plate-cathode circuits are very likely good to go. Overheated pots will cause loss of signal. That's the OD relay you're showing in the center of the photo... I think you need to wire it like this drawing. You have the contact sets switched relative to mine so I adjusted the drawing below to be close to what you have.

Thanks Martin. I will make the changes this afternoon and see where I'm at. That drawing is exactly what I need; I haven't researched the relays enough. Also, your low-plate photos were extremely helpful to me during this build. Thanks.

[martin manning]

See my edited post above re the V1 plates vs V2, and I revised my drawing. You may be okay, but I can't tell from your pic.

Also the white wire crossing the relay board (going to the top of the master, I assume) might pick up some noise from the relay coil.

[alvarezh]

Nice going Taylor, congrats!

I see that you are on the "detective" phase now, don't blame your work just yet. Do you know for sure that those tubes are good? Speaker and speaker cable good? Guitar cable? Sometimes simple things are the cause of problems, don't overlook them.

Get yourself a rag or something to protect from burning your fingers and move each tube in it's socket while you are hearing the cutout. Bad tube pin to socket contact can create a cutout.

I suggest trying the amp by phases, first your clean sound then try the PAB, leave OD sound for last.

Also, recheck your wiring on the input jacks, it gets complicated when the amp has the FET board.

Try going from preamp out to another amp to check if you still got cutout, that way you can tell if your problem is at the preamp or the power section.

BTW, your voltages seem to be about right, they are just a tiny bit low on some places, but nothing that could cause a cutout.

On the pots issue, I assume you mean that you think you over cooked them while soldering the shields to them. I am not an overly experienced person, perhaps they could eventually fail if you cook them, but I have never had a pot fail me by heating them too much. Never the less, if you have any suspects just check them in place, just desolder the leads.

[ToneMerc]

Taylor, this always I've always wired the AGB OD relay using a single MV.

TM

[martin manning]

TM, you show a redundant jumper there. Taylor has the connections to the left and right sides of the relay switched; not a problem if done correctly. His should look like my (revised) drawing.

[ToneMerc]

TM, you show a redundant jumper there. Taylor has the connections to the left and right sides of the relay switched; not a problem if done correctly. His should look like my (revised) drawing.

Martin, you are correct. The jumper under the board is for clarity in relationship to the HAD style board. I only run the one jumper between terminals 3 & 6.

TM

[amplifiednation]

Thanks guys! The amp fired right up when I changed the relay wiring. It is working perfectly. It already sounds pretty good. I'll bias it and fiddle around with some of the trim pots.

thanks to everyone for their help!!

oh, and this has to be the quietest amp i have!! and also the loudest