Marshall Valvestate 8280 Problems

[ove]

Since I'm new on the forum I would like to say hi to everybody

I have bought an old VS8280 which I'm trying to repair. My problem is the normal channel, the sound is very low here. I must turn the master volume to ten and grain on the normal channel to ten to hear some sound. On the OD 1 & OD 2 is the sound normal and very good.

What I have done:
- changed all the potmeteres
- I have set in a new tube
- cleaned all the connector pins

I have plugged the guitar into serial mono loop return jack and serial mono loop send jack. The sound is normal and good here too. I think the only problem is channel 1 normal.

Does anyone know what the problem can be?

Best Regards:
Svein Ove..

[ove]

Is there nobody here who can help me ?

[52 Bill]

Is there nobody here who can help me ?

Of course there are people here that can help you.

Was the channel working before you changed the pots?

Do you have a copy of the schematic?

There is a switching IC (5201) in your amp that would be the first thing that I would check.

[ove]

Of course there are people here that can help you.

Was the channel working before you changed the pots?

Do you have a copy of the schematic?

There is a switching IC (5201) in your amp that would be the first thing that I would check.

The channel was not working before I changed the pots. I changed the pots because they where bad.
I downloaded the shematic from Dr. Tube The dwg number is not exactly the same as the dwg number on my print cards ex. dwg no. 8280-63-02 and mine is 8280-63-00. On my power cc printcard there is no component in C15 & C17. These are not shown on the drawing either.

Is it the 5201 in IC 3 I should change?

[52 Bill]

Is it the 5201 in IC 3 I should change?

No, I would think IC4 which chooses between the two pre-amps would be the one to check first.

[ove]

Hi again,
Just arrived back from holiday. The parts was in the mail(5201)
I have changed the IC 3, 4, 6 & 2 and the amps are the same still low sound in normal channel. Do anyone have some ideas? Could it perhaps be IC 1? (TDA 2030)

Regards
Svein Ove

[52 Bill]

Could it perhaps be IC 1? (TDA 2030)

The TDA 2030 is an output chip and would not cause one channel to have a lower volume.

[ove]

Do you have some ideas?



Svein Ove

[52 Bill]

Do you have some ideas?



Svein Ove

Yes, check the clean/crunch switch SW1, Check the mosfet TR3 and most importantly recheck all of the pots and pc traces that you worked on when you replaced the pots.

[Enzo]

Look at the pots that are only used inthe low channel. Make sure the pots are the correct value - for example make suer you did not install a 100 ohm pot where a 100k pot belongs. ANd check any pot in that circuit to see if hte new pot was defective.

[shredwick]

I have a valvestate 8200, the 8280's big brother. My amp's clean level is also way lower and I've seen others with similar complaints. Try getting an eq pedal for when using clean channel or maybe try closing off the effects loops to adjust headroom. I use an eq thru the mono effects loop and another eq in my pedalboard. I still have to turn up the clean gain pretty high in comparison to the lead channel, though.