Help with a diode, MR 250

jochen.wendeba…

Tue, 03/25/2014 - 09:31

Music Man Amps Discussion Forum » Solid State Devices & Substitutions » Help with a diode, MR 250

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Josue Roberto Lopez Lobo (jorololo)
Username: jorololo
Registered: 01-2008

Posted on Wednesday, August 27, 2008 - 05:05 pm:

Hello, i need help with this diode MR 250/5, i have 210HD130-12AX7, in the manual appears 5KV A.I.V., physically says MR250/5, i want replace them, but anyone knows a good replace for this diode???

Bill Moore (bill_moore)
Username: bill_moore
Registered: 03-2013

Posted on Monday, March 18, 2013 - 04:25 pm:

did anyone source this diode?
Thanks

Lars Verholt (lmv)
Username: lmv
Registered: 11-2009

Posted on Monday, March 18, 2013 - 06:17 pm:

I've found an equivalent part: 1N1734A.
It seems to be available thorugh a couple of online distributors.
Hope this helps,
Lars Verholt

Bill Moore (bill_moore)
Username: bill_moore
Registered: 03-2013

Posted on Tuesday, March 19, 2013 - 09:32 am:

Thank you so much!

Bill Moore (bill_moore)
Username: bill_moore
Registered: 03-2013

Posted on Wednesday, March 27, 2013 - 02:45 pm:

I have been trying, but other than a $10 ea. 8 min order, I haven't found a source!
Was able to find the MR510 equivalent, and most of the caps through Mouser. Futurlec had the 16V zeners, and some other passive parts I need. A member on this forum is sending me the correct 400mf 25V caps.
Anyone have a couple they would part with?

Mike Kaus (mm210)
Username: mm210
Registered: 05-2006

Posted on Friday, March 29, 2013 - 08:05 am:

Not meaning to poke in here but what the hell schematic did you get that out of? I don't see any diodes like that in the 130 watt schem. All I see are the 1KV 3A diodes in the power supply area. Cheap. Maybe yours had a run that they got on sale somewhere but don't really think they are required. Export amp?

Mike Kaus (mm210)
Username: mm210
Registered: 05-2006

Posted on Friday, March 29, 2013 - 08:15 am:

Actually, I forgot about THOSE diodes. 5KV 2A. HMM. Don't have any of those.

Bill Moore (bill_moore)
Username: bill_moore
Registered: 03-2013

Posted on Friday, March 29, 2013 - 10:23 am:

Thanks for responding, Mike, I found a discussion that lists their purpose as protection for the OT from high voltage spikes. (believe it or not, from the speaker voice coil!) If I don't find any, I'll just use what I have if they test OK.

Full Name

gordon perry

Music Man Equipment

112RD 65 / G2 (I think)-6L6 model dated- 7/80

Member for

9 years 11 months

mr250 flyback diode

ogeecheeman Tue, 01/20/2015 - 04:03

anyone know if the fender 3000R diode is a suitable replacement?I have the 112RD 65 with 6L6 tubes

Full Name

Bill Moore

Member for

10 years 9 months

I ended up using the 3KV

bill_moore Tue, 01/20/2015 - 07:44

I ended up using the 3KV rated diodes in my RD100. I don't use it at high volume, (I've never even played it in "High"), but so far there is no problem.

Full Name

Mike Griffin

Music Man Equipment

MM 112-RD-65

Member for

10 years 9 months

3KV is OK

mgriffin155 Wed, 01/21/2015 - 17:01

Hi Bill,

The 3K PIV diodes are more than adequate. Go ahead and play it on Hi with confidence. They protect the output tubes and adjacent circuitry from a negative voltage spike if things go terribly wrong at the business end....like short circuited OT and/or speaker. $#!T happens when you're having fun.

Full Name

Bill Moore

Member for

10 years 9 months

Thanks for that!

bill_moore Wed, 01/21/2015 - 17:39

Thanks for that!
I haven't played out for years, and 100 W really isn't necessary in my music room, or in the living rooms we get together in. I figure the lower voltage on the tubes will keep it together longer anyway.
Although my friend Ted used it for years, somethings in 1K seat venues, and nobody had any problem hearing his Sho-Bud!

Music Man Equipment

112-75