MasterRoom / MicMix Spring Reverb - Fault Finding

[harry]

Hey Guys,

i know a couple of you have a MasterRoom Spring Reverb in use, and i was wondering if any of you have had any experience in fixing intermittent issues with them.

Mine is a stereo spring with a Model C controller (has Eq) and also have a spare controller (without eq).

It has never really worked right (damn ebay) so today i tried to get to the bottom of it:

Most of the time, the signal level is very weak, and no bass present (initially thought i had the hot / cold incorrectly wired) and also quite noisy.

but every time its turned on its different - today it was okay (full sound) but next power up, weak signal, no bass, hight noise floor.

I suspect that the cinch jones connector(s) and the round connectors that connect to the reverb tanks could be an issue as the plating has worn off a bit.

Does anyone anyone have a pinout or schematic info for these..

I started to re-cap the worse sounding control module (i have 2) and today it was sounding good, after a partial recap, the noise floor was better, then, next power up - same issues - no signal - no bass... even with the other controller..

the only constant are the cables that connect the tanks to the control units (remember i have 2 control units - one with eq one without) so it is strange that at different times, each control unit is fine, then goes bad..

how have your units been?

Cheers

[Sammas]

Finish recapping it! Any attempt to remedy the problem before finishing the recap will probably lead you to chasing your tail.

There are a number of test points in it, and probably some trimmers to control voltage rails and low frequency response. I would give the trimmers a spray with cleaner and exercise them a bit before recalibrating the unit after the recap.

[Alastair Reynolds]

Digging deep in the filing cabinet of obscure ancient schematics,I just so happen to have a complete original service manual for a MicMix Master-Room from 1974. I got it with a bunch of other old manuals that were being tossed out in the early 90s and wondered if I'd ever need it.Well that day has come.
Send me your email address and I'll fire up the scanner.
It covers the MR-II,MR-III and MR-IV .It may use some common design and would be a starting point as I imagine they just added a second tank and board and updated it a bit. In the meantime,I'll check some of my other files and see what turns up.
With the cabling,if it has Jones connectors with aluminum pins,try cleaning them really well. Aluminum will oxidize and develop high surface resistance that will cause all sorts of problems.

[dave01.cooper]

Alastair's audio manual book shop - catering to all those in need!!

[Alastair Reynolds]

For those of you old enough to remember him, Brian Murphy (RIP) who was at Syntec in the 70s, 80s, 90s 2K and at Rank and other such places before that taught me a lot about gear and never, never ,never chuck out a manual. You never know when you'll need it.
Consequently I started collecting and have ridiculous amounts of manuals , just waiting for when someone needs one.
I just need a bigger garage for that and the other gear that I simply can't live without.
I was also lucky to be given Brian's old Manual collection from his estate after he "racked his Cue" as it were.
My opinion:
share the knowledge and help others fix stuff, just as others did for me.
Kama will reward you

[Senad]

How good is this forum..!!?? Alastair:

[harry]

Hey Guys,

Thanks for all of your suggestions, and thanks for the schematics Alastair.

A full recap solved all of the issues associated with the unit. No more hiss or hum..

So then, I hard wired it into the rack / patch bay, hung it off some extra channels in cubase (as an external effect)

brought up the fader and ...damn.. 60hz Hum..

Funnily enough i thought it might be picking up hum from a transformer so i moved the rack and the hum progressively disappeared. But - the transformer was bolted to the rack (i.e. same distance)...

Then i figured it out - the unit hums if the electronics (control unit) is too close to the reverb tanks. Moving the reverb tanks 1 meter away makes the unit very very quiet.

Just thought i'd mention it in case any other master room users (there are a couple of us on this forum?) have a bit of hum coming through..

Thanks again for your suggestions..

[Lee]

Alastair you are a great bloke. I share the same thought about passing on information with others as people have done for me. The more good work people do the better the world is. As a young member on the forum I will aspire to be like that when I'm older...starting now.