peavey deuce transformers what to build

[bluesbreaker62]

I wouldn’t just assume HAD reused the old Peavey ‘choke’resistor.
It looks like this one might be 500R @ 10W while the Peavey resistor would have been 400R @ 10W

Here’s another example of an Overdrive Special that, I believe, uses Peavey Iron.
I have it down as being #80 but I’m not sure that’s correct. Anyone here know for sure?

Interesting amp anyway

80b.jpg

dumble_80a.jpg

love those chassis btw, clever

[Aaron]

I believe that's #155.
And, yes Peavey transformers.

Aaron

[norburybrook]

I wouldn’t just assume HAD reused the old Peavey ‘choke’resistor.
It looks like this one might be 500R @ 10W while the Peavey resistor would have been 400R @ 10W

Here’s another example of an Overdrive Special that, I believe, uses Peavey Iron.
I have it down as being #80 but I’m not sure that’s correct. Anyone here know for sure?

Interesting amp anyway

80b.jpg

dumble_80a.jpg

love those chassis btw, clever

sure, It just looked exactly the same make and model resistor that's all


are all these amp pictures from Rob Livesey's Dumble site/archive?

Marcus

[norburybrook]

I would get an impedance measurement on the OT. Just put some AC on the primary outer leads and measure that voltage and the voltage across the secondary: . Calculate that ratio, square it, and multiply the result by the specified impedance of the secondary tap you measured. Zpri = (Vpri/Vsec)^2*Zsec Even better if you put the appropriate resistor across the secondary when you do this. EL34's are 17% lower in Pa max than 6L6 so you are reducing the margin. The PT looks pretty stout, so it's not likely to sag much under load like some 100W Plexi's. That will add to the stress on the output tubes.

Rigth martin,

here we go.

Vprimary 9.9v AC
V secondary 0.65v Ac

9.9/0.65 ^2=231.9

231.9 *8(ohms)= 1,855

so does that make Zpri=1.85k?

and if so, what does that mean in respect to using 4 EL34's?

it seems close in spec to the Hammond 1650T: 120w- 1,900 C.T. Push-Pull Par. (4 or 6 Tubes) 6L6GC, 5881, EL34, 6550B, KT88.

Not sure how to calculate the plate and screen voltage/resistance stuff in relation to this.



marcus

[martin manning]

That's going to be tough for EL34's with 500V on the anodes. Max dissipation on that load line would be 67W, or 270% of 25W Pa max. With 30W 6L6 it would still be 225%, and it's not a good idea to let it go over 200%.

Did you have an 8R resistor on the secondary when you measured the OT? If not maybe try that and see if you get a higher Zpri. You are 240VAC normally there, right? The 370V on the schematic looks like it assumes 120V, and there is a 240V tap.

[norburybrook]

Martin,

I didn't have a resistor on the 8ohm tap no. I don't have an 8R resistor to try unfortunately. WOuld it go between the 8 ohm tap and the CT if I did?

My mains is usually around 245c AC in the studio.

I just used the AC outlet from a power supply which was giving 9.9v AC.


Obviously the transformers were working fine with the 4 x 6L6's in the combo so I would presume that I'm good to go with 4x 6L6's then regardless of what the OT primary resistance is, no?

I just fancied having a go at a #183 as it's the last one in the documented layouts I haven't built and I've not build an EL34 amp yet.


Marcus

[martin manning]

Yes it should be fine with 6L6's. In theory at least. The 8R would go from the 8 ohm tap to the common lead on the secondary, same leads as you measured the secondary voltage on.

[norburybrook]

which then begs the question would a 4x 6L6 #183 sound any/significantly different from a #102?

perhaps I should re think what to build maybe some kind of Marshall/express 6L6 perhaps.....

I've got a chassis and boards on hold from Taylor so need to make a decision.

Marcus

[martin manning]

I think there is much more coming from the preamp and the PI than from the power stage. People say that there is a difference between pentode and beam tetrode sound, and there probably is, but Dumble amps do not get their overdrive sound from their power amps.

[norburybrook]

I think there is much more coming from the preamp and the PI than from the power stage. People say that there is a difference between pentode and beam tetrode sound, and there probably is, but Dumble amps do not get their overdrive sound from their power amps.

good point Martin, and actually my mate Phil who got me into this in the first place always said (now I think about it); there's hardly any difference between output valves in these amps, he'd tried EL34 and 6L6's and heard no difference.

Right then, #183 with 6L6's it is then. Or I could have a bash at that #177 and use a resistor instead of a choke and the PI values mentioned.

can I just stick the 20-0 from that secondary into the regular rectifier board and then on to a 5 or 12v regulator as per normal? I'll use a full wave bridge rectifier for the HT and the normal bias rectifier which is showing -76vDC from the 56v tap, which should be fine I think.


I'll start a new thread about this when the chassis are finished and shipped.

thanks Martin

Marcus

[martin manning]

Yes send the 20V into a the relay supply's FWB. The 35V reservoir cap shown should be adequate. The relays don't draw much current, but I think with 20VAC input it'd be better to go with 12V relays so that the regulator drops less voltage.

[norburybrook]

Yes send the 20V into a the relay supply's FWB. The 35V reservoir cap shown should be adequate. The relays don't draw much current, but I think with 20VAC input it'd be better to go with 12V relays so that the regulator drops less voltage.

yes that was my thinking even thought the spec sheets show 35v max for both the 12 and 5v regulators. Obviously the 12v will be producing less heat as they're closer in voltage to start with.

I'm just keeping an eye on exchange rates at the moment , the whole BREXIT thing has had a terrible effect on sterling and things are now a lot more expensive when buying from the US than a couple of years ago, same with the euro.

M

[Aaron]

which then begs the question would a 4x 6L6 #183 sound any/significantly different from a #102?

https://youtu.be/wgp6amiiSfs

Here's a clip of Tag playing his #183, the TKT183 w/EL34's and I think TKT183 w/6L6's.
Sounds pretty damn good with 6L6's to me.

Aaron

[norburybrook]

Yes 6L6 sound much better to me [emoji16]

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