[HELP] I need a little bit of Backup with my Marshall.

[QSQCaito]

Hello guys Long ago my cousing gave me his marshall 8010 valvestate, he wasn't playing any longer. It was working bad, all pots were noisy, and in certain position (50% master volume) you started hearing a loud PIIIIIIIIIIIIIIIIIIIIII. Yesterday I got on its guts. First of all, there is no valve in the preamp, as some valvestate have. It's fairly simple, everything pcb mounted. I'm going to change all the pots (although I don't know If i'll get the 22k pots, I'll just repllace ot with 25k ), I'll also change the input jack, which was a bit failing.

While watching the schem (Marshall 8010 Schematic.) I realize I didn't understand what was going on in the power section. First of all, in the transformer there are 7 wires, 3 on the bottom, 4 on the top, can't understand why so many. In the diode bridge, 3 nods are labelled -, one is labelled + :S

Last, but not least. Do you believe any improvement could be made to this little monster? A new op-amp, a newer tda?


Thanks!

Bye

DAC


EDIT: Sorry for this mis-use of the forum.

[slideman82]

COmo andas Diego! Si pones los de 25k no pasa nada, dale para adelante, es mas, si los medis, van a ser como de 22k mas o menos! No se si se le puede hacer algo a ese valvestate, a partir de 40W tiene la valvula tanto los MKI como los MKII (el 8040 a mi gusto suena terrible!). Si queres proba con un TDA2050, que es emjro que el 2030, es de mas potencia, pero con la baja tension que tenes no va a tirar los 25 o 30W que declara. Lo que si me parece raro es lo del trafo, que tenga varios cables.

El ampli es tuyo?

[QSQCaito]

Buenisimo

Let's keep in english for the ppl

He suggetsed maybe changing the tda for a 2050m basically.

The transformer seems weird to me too, and yes, it's mine

[slideman82]

Ok, let's write in English, but I think is the same. If someone doesn't understand, ask any of us, please. Well, I suggest you to build other amp instead of it. Maybe you can get a better sound from better components. It has to be something easy, simple, but great! I suggest you to try this as power amp:
http://www.redcircuits.com/Page123.htm . I don't know how good could the preamp sound, but I'm sure power MOSFETs will do the work perfectly.

I suggest this because I don't like opamps in guitar circuitry, well, just for amps or distortion.

[QSQCaito]

Hehe.. I'm keeping this original

Did a search in local eBay, and its' worth 370 pesos argentinos, used. It's english, around year 1991.

That's around 120USD. Which's a lot! and it was a gift!

[slideman82]

AAAAAAaaaaaaaah ok, si era un regalo, es otra cosa! Si, a veces esta bueno dejarlo asi. Suele pasar que se queman los 2030 o 2050 o similar, si esto pasa alguna vez, poner un 2050, tiene mejor calidad. Saludos