Also about three weeks ago...
Took the bottom panel off to get to the mixer PCB's and look at the underside of the transport...nice heavy-guage panel on the bottom...comes off with little time expense and exposes everything
. See here...transport in the right, mixer on the left...this is how you get to the capstan belt to change it and it is very easy. Look for shedshrine's dedicated tutorial
to changing out the capstan belt. Excellent detailed steps and photos...here's the photo of the inside of my 388's belly:
What I found under there (outside of some dust-bunnies) was clean and intact. Capstan belt looks and feels really nice...capstan pulleys are very nicely crafted pieces:
BUT...I noticed some runout (wobble) on the capstan motor pulley..."uh-oh" I thought...is my capstan motor shaft tweaked? I got out my trusty $15 guage with magnetic mount (don't worry folks...no tape in sight and the headblock was already pulled
) to test both pulleys and ultimately the capstan motor shaft...mount, adjust, spin and watch the dial:
What I found was that the face of the capstan motor pulley was wobbling by about 0.002". The casptan shaft
pulley was dead-steady, as was the capstan motor shaft!
The capstan motor pulley mounts with two set screws oriented at 90-degrees to each other like the reel tables and such so my guess is that the wobble was the by-product of how the pulley mounts. I'll try to get it as steady as possible when I put it back together. AND...keep in mind that the belt likely acts as a damper to such vibrations that might be caused by that slight wobble AND the heavy capstan shaft pulley is going to dampen as well. My guess is that that 0.002" wobble has an immeasurable effect on performance, but you know me...If I can get it to be less I will. If not I figure it has probably been that way since they put the thing together.
As I mentioned I took the headblock off to inspect it, clean it and get it out of harms way during other activities. Here are some closeups...Note that the shield for the record/repro head is loose, and what is that wierd light smudginess on tracks 1&2 and 7&8 on the record/repro head???
Here are some after shots of things, and, no, the smudginess didn't come out......I'd like any input on that that I can get. Anybody else seen anything like that?
Also pulled mixer cards and doing the usual inspecting, cleaning and recapping...its funny how easy it seems to recap these channel cards...there are 14 caps compared to the M-520's 24, which may not seem like a big difference, but it feels
so much quicker and easier...plus there is lots of room around the caps and there aren't wires to manipulate sitting over caps (like on the M-___...that's a PITA...and 73 caps per channel strip on THAT...
) Okay...I know, I know. Overkill right? Hey...Its 20-some years old. It can't hurt...I have the caps on-hand that are doing nothing but aging otherwise and I've got to do SOMETHING to live up to my custom "Don't bug me; I'm recapping" t-shirt. Kidding.
Here's a 388 channel card cleaned, inspected and recapped:
Stay tuned for the next installment!