Valvestate VS100 Modding?

[Toepolev]

Hello.
I've just bought a second hand Marshall VS100 (8100) and was checking if everything was alright inside.
I found out that the two cap's C61 and C62 (2200µF) had a high head on, so I want to change them aswell as the other two C40 & 41 (1000µF)
I was wondering if it would do any good to put in higher values, resp. 3300µF and 1500µF. Because they are buffers to soften the ripplen higher values are better. Is there anyone who thinks this is a bad idea?

Second thing:
I would like to change one of the two red led's, that indicate the boost, into a blue one. Measering the value of the led, it starts shinning at 1,5 volts. My blue led starts at 3V. When I check the schematics, I see that it is getting his current from a bridge of two resitors 1k5 connected to the 15V supply.
I calculated that I would have to change these two R's into 1k33.
Would that change anything in the circuitery?

[Enzo]

It won't hurt anything to increase those caps, but it probably won't help any either. The amps are not especially hummy from power supply ripple. Most hum you get will be from grounding and connection problems. But why not? Go ahead.

LEDs. Try the blue one in there now, it might light up with the resistors in there now. Those resistors are working with the natural voltage across the LED to limit current through it. They do not in and of themselves set the voltage for any random component.

Your change is very small, and probably won't affect the switching circuit. But the upper 1k5 resistor is also a pullup for the base of TR1. SO we want to keep that in mind. If I were making a resistor change, I would change the lower resistor only, and change it by the full amount instead of half the amount at each resistor.

I don't know if the blue LED needs a different amount of current than the red. if it were me, I'd look at the data sheet for the LED for current. ANd the simplest thing to do would be connect a small pot in place of the lower resistor (R9?), maybe 2k, and dial in the best LED voltage. Then remove the trim pot and measure its resistance. Install a resistor of a similar value to the measurement.

[Toepolev]

Thank you Enzo for your info.
About the led's, I was thinking something in the same direction. I just wasn't shure if the circuit was set up for a reference-voltage. I will try just changing the led, maybe it'll work fine.
About the hum: I bought mine second hand and when I turned it on, there was a slight hum that was cycling around. It was like it was superimposed on a wave. It wasn't very hard, but still, I watched the elco's and one's head was fat so I will change them all.
Are there modifications to do on this amp that would improve something?
Thanks again and sorry for eventual mistakes in the English I write: I am living in Belgium, Flanders so English is something I don't use everyday.
Greeting,
Tony

[Steve Conner]

Before you change the capacitors, try poking the "fat head". Some electrolytics have a black plastic disc on top that sometimes bulges up and makes the capacitor look bad. But if you can press it down easily, it's probably OK.

Of course changing electrolytic capacitors every 10 years or so never does any harm...

BTW, blue LEDs tend to be very bright even at low currents. You'll probably find that it works fine without changing the resistors.

[Toepolev]

Thank you Steve.
This cap doesn't have a plastic cap, its the metal head thats sticking up.
I already bought new ones, doesn't cost much
I will try the blue led's without changing te R's, think it will work to.
Greetz,

Tony

[Toepolev]

Blue Led works fine!!!


Hello reader.
I placed the new caps and blue LED without changing any resistor and it works fine.
Thanks to all who repleyed with info.
Greetings,

Tony