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Help on Marshall Bass State B65 transformer

PostPosted: 05 Feb 2014, 13:00
by arcaarca
Hi everyone,
a friend of mine gave me a Marshall Bass State B65 combo. The transformer is broken, it's a Dagnall transformer type D9609.
The final stage of this amp is very similar to Valvestate V65 amp, whit T64-T65 power transistors:

http://www.drtube.com/schematics/marshall/pc0689p.pdf

one of the mainly differences is the couple of resistors R101-R102, they are 470 ohm in B65.
The trafo specifications for Valvestate 65 are Dagnall D9601 or Drake 784-352

I need some help on get the transformer specifications, I think it could be a 24-0-24 or maybe little more, but I'm not so good with trafo stuff and I'd like start to learn something ;-)

Thanks a lot

Re: Help on Marshall Bass State B65 transformer

PostPosted: 07 Feb 2014, 12:31
by phatt
Your description of problem is a bit vague,
Can I ask How you established that the transformer has blown?
Have you checked FS1 ? (the mains fuse)
Phil.

Re: Help on Marshall Bass State B65 transformer

PostPosted: 07 Feb 2014, 12:44
by DrNomis
arcaarca wrote:Hi everyone,
a friend of mine gave me a Marshall Bass State B65 combo. The transformer is broken, it's a Dagnall transformer type D9609.
The final stage of this amp is very similar to Valvestate V65 amp, whit T64-T65 power transistors:

http://www.drtube.com/schematics/marshall/pc0689p.pdf

one of the mainly differences is the couple of resistors R101-R102, they are 470 ohm in B65.
The trafo specifications for Valvestate 65 are Dagnall D9601 or Drake 784-352

I need some help on get the transformer specifications, I think it could be a 24-0-24 or maybe little more, but I'm not so good with trafo stuff and I'd like start to learn something ;-)

Thanks a lot



Have you tried googling for the specs for that transformer?...... :hmmm:

Re: Help on Marshall Bass State B65 transformer

PostPosted: 08 Feb 2014, 17:59
by arcaarca
to Phatt: I've checked main fuse, it was blown and it blowns when I turn on the main switch, even if I use only the transformer, removing the wires from secondary to pcb, so I think the problem should be on the transformer,

to DrNomis: I'm still googling around, I found many specifications for other Dagnall transformers, but no one for the D9609 or D96.. series :x

Full description on the transformer is:

TX3
D9609 9546
Dagnall Electronics Ltd

Re: Help on Marshall Bass State B65 transformer

PostPosted: 08 Feb 2014, 22:59
by phatt
OK, yes sounds terminal but it still could be a faulty power switch. I'd Try removing it from circuit before I give up. (assuming switch is after fuse)
If Transformer then yes likely the circuit runs from 35~40 volt DC rails so any Transformer that outputs 25~28 x2 VAC will likely make it work again.

Time to hunt down old stereo equipment that are often now collecting dust or trashed at the local tip. :secret:
Phil.

Re: Help on Marshall Bass State B65 transformer

PostPosted: 09 Feb 2014, 00:25
by deltafred
To give 65W at 8 ohms you need a minimum transformer voltage of about 24v for each winding with a total current of at least 3A (1.5A per winding). Probably best to go a bit higher on the current so you don't cook the transformer, 2A per winding should be fine.

So as Phatt says about 25v or a bit more, don't go too high otherwise you will be needing a new speaker (driver) if you get a bit carried away with the volume control.

Re: Help on Marshall Bass State B65 transformer

PostPosted: 12 Feb 2014, 17:58
by arcaarca
The fuse is after the power switch, and before the transformer, so I think the problem is "just" the transformer.. sigh!!
I'll have to looking for some good stuff, maybe 2nd hand store or similar... thanks a lot to everyone for suggestions and support!

Re: Help on Marshall Bass State B65 transformer

PostPosted: 12 Jan 2018, 01:55
by ilcaccillo
phatt wrote:OK, yes sounds terminal but it still could be a faulty power switch. I'd Try removing it from circuit before I give up. (assuming switch is after fuse)
If Transformer then yes likely the circuit runs from 35~40 volt DC rails so any Transformer that outputs 25~28 x2 VAC will likely make it work again.

Time to hunt down old stereo equipment that are often now collecting dust or trashed at the local tip. :secret:
Phil.


In the schematic the rails are +15V and -15V and not "35~40 volt DC rails"

Re: Help on Marshall Bass State B65 transformer

PostPosted: 12 Jan 2018, 02:42
by Ice-9
It is probably a close spec Tx to the V65 but as you have only posted the part of the schematic for the V65 and not the bas state B65 and I am unable to find the correct schematic for the B65 it is not possible to say. Your easiest solution would be to email either Drake or Marshall for the Tx spec. I have had regular dealings with Marshall and always have had them give me the info needed. They have even sold me replacement transformers for JMP1's. Give them an email, probs the quickest answer you will get.

PS , i'm guessing by its model name it has a preamp valve, so the TX will have multiple windings for high voltage and heaters for the valve and low voltage windings for solid state circuits. Marshall generally use +/- 15V DC for op amp parts and somewhere between +/-25V to +/-35V for the output stages.

Re: Help on Marshall Bass State B65 transformer

PostPosted: 12 Jan 2018, 10:02
by Manfred
I had have a Valvestate V80 for repair in the past, parts of the power supply are the same as these in the V65.
I noted down the read voltages.
V80_1.jpg

V80_2.jpg

Re: Help on Marshall Bass State B65 transformer

PostPosted: 06 Feb 2018, 01:02
by ilcaccillo
Ohh I see,
thats correct, thanks for clearing this up