Marshall Valvestate 8080 and Laney tf200 Power transformers missing! - diyAudio
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Old 8th May 2012, 08:23 PM   #1
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Default Marshall Valvestate 8080 and Laney tf200 Power transformers missing!

Hello everyone!

Last week a friend of mine brought to me 2 amps that he found somewhere. It was a marshall valvestate 8080 and a Laney tf200. They are both in good condition. Their only problem is that they are both missing their power transformers...
I would like to fix them and test if everything works fine!
I found a lot of schematics on the web, but none of those where writing the exact features of the transformers...
Does anyone knows to tell me all the needed features and specifications from the transformers of those two amps?

Thanks anyway!!
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Old 8th May 2012, 11:55 PM   #2
nazaroo is offline nazaroo  Canada
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Quote:
Originally Posted by Lina View Post
Hello everyone!

Last week a friend of mine brought to me 2 amps that he found somewhere. It was a marshall valvestate 8080 and a Laney tf200. They are both in good condition. Their only problem is that they are both missing their power transformers...
I would like to fix them and test if everything works fine!
I found a lot of schematics on the web, but none of those where writing the exact features of the transformers...
Does anyone knows to tell me all the needed features and specifications from the transformers of those two amps?

Thanks anyway!!
This is a solid state 'tube-emulating' amp, right?

Could it be similar in power/voltage to either a Fender S.S. "Twin" type amp, or even a 60 watt Fender Rumble 60?
Because I have the transformer for the "Twin", shows 72 volts c.t. (no load), and the other one is used (in the Rumble) to run a 'chip amp' power section.

Point is, I could ship these to you if you for say, $30 / transformer, + shipping to USA, = about $30 S.H.
i.e., $60 each?
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Old 8th May 2012, 11:58 PM   #3
nazaroo is offline nazaroo  Canada
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Here is the schematic...

One thing I notice is that the Power Supply is programmed for failure,
with crappy 16v 1000uF caps at the output of the +- 15 volt supply!

These should be at least 30v 1000uF (and must be replaced before they go if they're not gone already).

They have 50v caps in the first stage of the Pie Filter, so they know they're idiots here.
Maybe the idea is to always have these filter-caps blow first, for easy repair money.

The voltages suggest that the power transformer is a 32-35v c.t. (16-0-16) under load.
Someone knowledgeable about transistors could tell you what current (VA) rating the tranny should be,
by calculating the current draw of the amp.
Attached Files
File Type: pdf Marshall valvestate80_80w_.pdf (176.8 KB, 20 views)

Last edited by nazaroo; 9th May 2012 at 12:09 AM.
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Old 9th May 2012, 12:47 AM   #4
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Came across a site where someone measured their power amp voltages and they were +/- 40V. Not confirmed mind you.
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Old 9th May 2012, 11:00 AM   #5
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Thanks a lot both of you! The truth is that im not very good with all these things and i dont want to destroy it because of a stupid mistake!
Here is the schematic from the Laney

http://www.freeinfosociety.com/elect...efusion200.pdf

If you could see this too and tell me your opinion, it would be very usefull!! THANKS!!!

Last edited by Lina; 9th May 2012 at 11:22 AM.
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Old 28th November 2012, 07:02 PM   #6
JMFahey is offline JMFahey  Argentina
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Quote:
One thing I notice is that the Power Supply is programmed for failure,
with crappy 16v 1000uF caps at the output of the +- 15 volt supply!

These should be at least 30v 1000uF (and must be replaced before they go if they're not gone already).
Well, not exactly.
Both Marshall and Laney (and thousands others) suceed in using 16V caps on 15V lines, because having extra voltage rating in this particular case is not necessary.
Most PSUs must be happy with +15/20% line voltage, so upgrading by that amount or a little more never hurts ... but here we have Zener regulators, so that will never be an issue.
Of course, going to the next normalized voltage, 25>V, adds little to cost.

Quote:
They have 50v caps in the first stage of the Pie Filter, so they know they're idiots here.
No, they have 50V caps here because it's an about 40V supply, unregulated, so 20% extra is fine.
Quote:
Maybe the idea is to always have these filter-caps blow first, for easy repair money.
Well, repairs are money *LOSS* to Manufacturing Companies, and it's them who decide what's used, not your neighbourhood Tech.
Quote:
The voltages suggest that the power transformer is a 32-35v c.t. (16-0-16) under load.
No, +/-40V rails suggest 28+28V to 30+30V 120VA or better PT for the Marshall; 20/22Vx2 60/80VA for Laney.
Quote:
Someone knowledgeable about transistors could tell you what current (VA) rating the tranny should be,
by calculating the current draw of the amp.
Answered above.

Last edited by JMFahey; 28th November 2012 at 07:05 PM.
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