Studio Preamp LDR

Triaxis, Quad Preamp, Stereo Power series, Recto Preamp

Moderators: Guitarzan, Grandor, ned

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Electricsun
Bottle Rocket
Posts: 3
Joined: Tue Oct 25, 2016 7:26 pm

Studio Preamp LDR

Post by Electricsun » Sat Dec 02, 2017 11:25 am

Hi, I think this is my first thread here, but my account is not new.

Can you please help me identify these LDR models?

The preamp is a Studio Preamp, Serial Number SP1060

I’ve been reading a lot about a problem I have with the drive channel leaking sound into the clean channel, and I’m almost certain that the problem could be the LDR, as also confirmed by Mesa/Boogie staff by email.

I thought about sending to repairman, but here in Japan is just so expensive to have a repair, even if I just need them to do an specific job (changing LDR) the repair shop won’t receive the preamp unless I do overhaul first (about $150)

So, putting all the fees altogether is almost the price I paid for the unit, so I just want to try repair myself :mrgreen:

Are these the rights equivalents?

Photos inside link

https://imgur.com/a/5G5oc


I’ll go soon to the electronic shop (in akihabara!) hoping they have the parts.


On a second note, are these too difficult to take from the PCB?

It’s not easy access, but I’m guessing I just need to desolder from the top and just replace, right?

Thanks for your time, any help is appreciated!

Electricsun
Bottle Rocket
Posts: 3
Joined: Tue Oct 25, 2016 7:26 pm

Re: Studio Preamp LDR

Post by Electricsun » Sat Dec 02, 2017 11:32 am

Sorry I forgot to add, I think it’s

LDR1 and LDR2 is 21L883
LDR3 is 21L884
LDR4 is the Vactec Vactrol

21L884 = VTL5C4
21L883 = VTL5C1
Vactec Vactrol = VTL5C1

MesaMad1378
Mark II
Posts: 61
Joined: Tue Sep 15, 2015 4:49 pm
Location: Gold Coast, Australia

Re: Studio Preamp LDR

Post by MesaMad1378 » Fri Dec 15, 2017 7:41 pm

Hi there,

Does it look like they have been replaced before? I'd like to know if someone has used these in a 2:90 as well?

They have different current and voltages to the VTL5C9 that the 2:90 has in it.
Mesa Dual Rectifier, TriAxis, Recto Recording,
2:90, 2:100, SUS-4 16ru Case,
Flux Five, Throttle Box EQ, 5 Band EQ,
Straight Traditional 4x12 Cabs.
And other stuff!!

Electricsun
Bottle Rocket
Posts: 3
Joined: Tue Oct 25, 2016 7:26 pm

Re: Studio Preamp LDR

Post by Electricsun » Tue Jan 02, 2018 7:31 pm

MesaMad1378 wrote:Hi there,

Does it look like they have been replaced before? I'd like to know if someone has used these in a 2:90 as well?

They have different current and voltages to the VTL5C9 that the 2:90 has in it.
Thanks for your reply!

When I looked into it it didn’t seem they had been replaced. I got this unit from a friend for about $200, and he got it used from another person, so I can’t really tell how it was used.

Do you think I could be making a mistake trying to replace them with similar values of LDR?

I thought about buying from Cabin Tech website

MesaMad1378
Mark II
Posts: 61
Joined: Tue Sep 15, 2015 4:49 pm
Location: Gold Coast, Australia

Re: Studio Preamp LDR

Post by MesaMad1378 » Wed Jan 03, 2018 7:57 am

Those numbers you have would probably be right, I’ve seen other vactrols used in other Mesa Amps, such as the Triaxis, I haven’t seen other brands, though I haven’t had the please of playing around in all Mesa Amps yet. Definitely would not mind though.
Mesa Dual Rectifier, TriAxis, Recto Recording,
2:90, 2:100, SUS-4 16ru Case,
Flux Five, Throttle Box EQ, 5 Band EQ,
Straight Traditional 4x12 Cabs.
And other stuff!!

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