Function of AVC-1 unit on MRA1-L6

[PatrikD]

Hello

i tried to google and searched this forum but no good result, on my my amp there is a AVC-1 (Automatic Volume Compensator), can someone explain to me the function and use of this unit?

Best Regards

Patrik

[Ron Rich]

Hi Patrik,
That was an "optional" addition (which also requires a switch be added on the mechanism) on that model amp, to provide "compensation" for different volume levels on the records--The idea is to keep some records recorded at volumes below the standards, and others, recorded at levels above the standards, to sound equal when played. Hope that helps , Ron Rich

[PatrikD]

Thanks for the answer Ron, next question is the AVC needed to have the amp running ? Mine AVC is missing 2 tubes :-(

Patrik

[Ron Rich]

Hi Patrik,
I am now confuzzed--do you have a MRA-1, with the added, AVC component, or, do you have a later (MRA-3 ++) model with the AVC tubes removed. If the later, yes, the amp will function minus those tubes. If a MRA-1, with AVC, I don't know for sure ? Without an added AVC unit, I don't think a -1 can function, with any missing tubes ? Ron Rich

[PatrikD]

Its an MRA1-L6 with an AVC-1 mounted on it, the AVC have three tube socets in it :-) (and i missing 2 of the tubes)

[Ron Rich]

I am not sure, in this case--which AVC was added --early, or late version (before serial # 1969, or after that number)?

[PatrikD]

The seriealnumber on the amp is 10987, this is not the original amp for the box (100B), there is also an socker for an 3 contact, and that connection o dont have from the mech (i supose it would come from the mech)...do anyone here on the forum have an picture what kind of connection on the mech this should be), Ron, do your service manual cover AVC-1 ”kit”

Patrik

[Ron Rich]

Hi Patrik,
There should be a serial number on the AVC kit, itself. You need to use the three prong socket, ON, the AVC unit--the one on the amp is eliminated when the AVC is installed. The plug for that socket has the mute, ground, and AVC squelch wires, in it, from the mechanism.
I have written two SUPPLEMENT GUIDES, not manuals, for Seeburg phonograph products. The one appropriate for all models is the "Seeburg Mechanism Guide". This covers ONLY the mechanism, and some brief info on the 4 different selection systems used over the years, as related only to the mechanism. The other one is "the Seeburg MicroLog Trouble Shooting Guide". This covers the late 1970 -1978 "MicroLog selection system, they used them. Ron Rich

[PatrikD]

Thanks Ron, if i understand this right with some more readings and with an manual i found, this AVC-1 is just an plugin module to the Amp, there should be nothing alterned in the Amp itself for the Module to work, if i dont want the AVS i just unplug it and replace it with the orginal tube.



Regards

Patrik

[Ron Rich]

Hi Patrik,
Unfortunately NO--- if correctly installed, parts under the chassis were to be cut-- if there is a paper label on the AVC, it will show that.
Also-- without the "box", the amp WILL "hum" ! Ron Rich

[PatrikD]

Hi Ron

I removed the AVC now and on the side there was as you write an instruction what is alterned on the amp, gonna buy the tubes and try, both the amp and also the AVC has new capacistors on it (rebuilded in the States and importens to Sweden).Serial number on the AVC 3863


Regards

Patrik