Marshall Integrated Bass System 5510

[marklim]

Hi, I really need some info. I am repairing a Marshall IBS 5510. It's got a blown transformer (Drake 7-200/6). Since it's an 80s model, I need to find a suitable replacement.

Could anyone tell me the secondary voltage of the tranny (I am guessing either 35 or 50v) and also the power rating required (VA)?

Any info is greatly appreciated.

Many thanks.

[soundguruman]

whats the voltage rating of the power supply caps?
whats the size of the mains fuse?
Whats the power output rating?
Rated into what load?
With that info you can determine a power tranny, just about

like for instance if the power supply filters are 63 volt
I know this is about 50 volt power DC
And if the filters are 50 volt, I know the voltage of DC is going to be about 35

Nobody is going to build 50 volt caps for a 50 volt supply, certainly not Marshall

But what made the power tranny blow in the first place?
Do you have shorted output transistors?
Shorted rectifier?

[marklim]

whats the voltage rating of the power supply caps?
whats the size of the mains fuse?
Whats the power output rating?
Rated into what load?
With that info you can determine a power tranny, just about

like for instance if the power supply filters are 63 volt
I know this is about 50 volt power DC
And if the filters are 50 volt, I know the voltage of DC is going to be about 35

Nobody is going to build 50 volt caps for a 50 volt supply, certainly not Marshall

But what made the power tranny blow in the first place?
Do you have shorted output transistors?
Shorted rectifier?

Many thanks for the reply. I am guessing it blew due to shorted rectifier bridge. But I plan on rebuilding the entire PS section anyways.
Output FETs will also be changed.
I have the schematics, though it doesn't state the voltage for the secondary on the tranny.
Any guesses? I am quite certain abt 50V DC is required to get approx 100W out of the J49 and K134 FETs.
The only issue is the AC V from the tranny to the rectifier.
These are the schematics for the Preamp and PS/Output.

3510pwr.pdf

Thanks again

[Steve Conner]

Given that the thing runs one pair of those Hitachi MOSFETs, I'd recommend a transformer of roughly 2x 35V, and about 160VA. That's what was in my old Maplin Mosfet amp with the same output devices. It's not really critical though.

The DC voltage out of the rectifier is roughly 1.4x the AC input.

[marklim]

Given that the thing runs one pair of those Hitachi MOSFETs, I'd recommend a transformer of roughly 2x 35V, and about 160VA. That's what was in my old Maplin Mosfet amp with the same output devices. It's not really critical though.

The DC voltage out of the rectifier is roughly 1.4x the AC input.

Thanks Steve. I agree, probably 35v. Do you think that would work out to the 15v on the preamp side?

[Steve Conner]

Yes, the 15V is regulated by Zener diodes.

[marklim]

Yes, the 15V is regulated by Zener diodes.

Thanks Steve. You have been most helpful. Based on other research, I am pretty sure it's 35V X 2. Looking at the size of the original tranny, I guess 160 - 200 VA.

[marklim]

whats the voltage rating of the power supply caps?
whats the size of the mains fuse?
Whats the power output rating?
Rated into what load?
With that info you can determine a power tranny, just about

like for instance if the power supply filters are 63 volt
I know this is about 50 volt power DC
And if the filters are 50 volt, I know the voltage of DC is going to be about 35

Nobody is going to build 50 volt caps for a 50 volt supply, certainly not Marshall

But what made the power tranny blow in the first place?
Do you have shorted output transistors?
Shorted rectifier?

Hi Soundguru,

Voltage rating of PS caps is 63V.
Mains fuse is 1.5A
Output rating 100W into 4ohms

So, what do you reckon? Secondary 25v X 2 or 35v X 2?

Thanks

[Steve Conner]

Well, it would probably run fine anywhere between 25V and 35V, it is just a question of how hard you want to push the power amp. My Maplin Mosfet amp was rated 160W into 4 ohms using the same devices and a 2x35V transformer.

100W into 4 ohms implies 2x28V and I think it would be more robust and "gig proof" at that voltage: 160W was really pushing it. I'd go for the nearest stock voltage to 28V: maybe 30V.

[marklim]

Thanks Steve.

Gonna quote the customer to see if the $$ is worth it

Will let you know the outcome.

[Jazz P Bass]

The Hammond 165P30 should do fine.

[Steve Conner]

Reading between the lines, this guy is in the UK and looking for a toroidal transformer. RS and Farnell both carry a selection.

[marklim]

Hahaha... Steve, I am actually in Malaysia...
I can actually get a pair of the original Japan made Hitachi 2SK49 and 2SJ134 for around US29 from my local supplier.
For the toroidal, I'll be getting from Farnell.

Thanks again mate!