Marhsall 1962 Bluesbreaker reissue - low power problem

[Chuck H]

This one is said to sound good. It costs less and being a Hammond product it should be very reliable.

1750Q Hammond Manufacturing | 1750Q-ND | DigiKey

[Jazz P Bass]

The Drake 784 389 was used in the RI amp, also.
The JTM45 reissue amp OT's expect a 5881 or a KT66 pair don't they?

[Chuck H]

The Drake 784 389 was used in the RI amp, also.
The JTM45 reissue amp OT's expect a 5881 or a KT66 pair don't they?

Yes. Something different. Like 7.3k primary Z.

[drewl]

Dang, I forgot Digikey was carrying Hammonds.

[binito]

Yes. Something different. Like 7.3k primary Z.

uses two 5881.
the original transformer is a d2505 dagnall.
that impedance is this?
The drake 389 that impedance has and valves works?

[nickb]

uses two 5881.
the original transformer is a d2505 dagnall.
that impedance is this?
The drake 389 that impedance has and valves works?

Dagnall were reborn and still have all the drawings for these. Since you're in the EU why not email them and get a quote?
Dagnall Electronics - Transformers

[binito]

Dagnall were reborn and still have all the drawings for these. Since you're in the EU why not email them and get a quote?
Dagnall Electronics - Transformers

Dagnall does not sell to end users spare parts of marshall. only can be purchased from an authorized dealer.
I can get the original in WWW.tubetown.de, but I'd like to know the impedance differences that exist to 5881, kt66 and el34?

[TimmyP1955]

Are you sure about the bias? There's a lot of crossover wonkiness on the output. Also try it with other loads - the wrong load can give you a trace like that.

For transformers, try Marshall Style Transformers By ClassicTone

[drewl]

Dagnall does not sell to end users spare parts of marshall. only can be purchased from an authorized dealer.
I can get the original in WWW.tubetown.de, but I'd like to know the impedance differences that exist to 5881, kt66 and el34?

If you go to tubesanmore.com they have specs on all the different output transformers, size, impedance etc.
Then you can figure out which one you need and can purchase locally.

Some have different taps so they can be used with either 6L6's or EL34's.

Replaced the output trans in a JCM 900 this week with same symptoms you are experiencing.

[Jazz P Bass]

Are you sure about the bias? There's a lot of crossover wonkiness on the output. Also try it with other loads - the wrong load can give you a trace like that.

If you look at the plate o'scope capture, the OT secondary basically is a reflection of the plate 'wonkiness'.
It is as if the plates are trying to drive a very weird load. (ie: bad winding)
I vote bad OT.

Then again, if it was on my bench I would slap in any old OT on hand to prove it.
The OP apparently does not have this luxury.

[binito]

Was Output transformer. I change and now the volume is ok.
Now 600V p-p in plates of power tubes. And 40V p-p in 8ohm output.

[Randall]

Good call, binito.

[nickb]

Dagnall does not sell to end users spare parts of marshall. only can be purchased from an authorized dealer.
I can get the original in WWW.tubetown.de, but I'd like to know the impedance differences that exist to 5881, kt66 and el34?

Glad you got it all worked out

Just in case anyone else is looking at this thread in the future, it took a while to hear back from Dagnall but they do have the same transformer available. They can't sell the actual one but they tell me they have an identical non-Marshall for around £43 inc shipping.