Rowe AMI R-90 wiring and intermittent hum

I recently purchased a Rowe R-90 and have been going through everything. Previous owner picked it up in a warehouse sale with other items and knew nothing about it. I think he may have "tinkered" with it a little, but for the most part it looks like it hasn't been touched in a few years.

I replaced the CCC battery and had to perform all adjustments regarding the tonearm (someone had replaced the cartridge, installed it backwards and screwed up everything else). At this point, I think I have most everything working correctly and just need to replace the woofers. That's all the history I have up to today.

While going through this, I've noticed what I consider to be an excess of 3M quicklink connectors on various wires (IMHO, one is excessive, but this has well over 20). They're all over the place. Some them have faded in color to almost white while others are still reddish. Some are easy to get to and some are actually bundled up it what looks like the original wiring harnesses, like they were used at the factory. My question: were these normally used in assembly or accepted at one time for repair/troubleshooting by Rowe AMI? I'd be less concerned if this is normal, but I really suspect this indicates some questionable service history.

The only other item that has been making me a little nuts is an intermittent humming. If the machine just sits for a while, anywhere from 10-30 minutes, I'll hear a hum and then it will stop. It's not coming from the speakers, amp or any of the transformers I can find. I'm pretty sure it's coming from somewhere in the mech assembly. It sounds like maybe a solenoid or motor, but I can't locate it. There's no vibration from anywhere I've been able to touch and nothing seems to be getting warm. If it's very quiet, I can sometimes hear what sounds like the records shook a little, then the hum will show up right after. I've watched while this happened, but have yet to see anything "move". I'll wiggle, shake and poke anything I can find in the mech while it's humming, but if it stops when I do something in particular, it won't necessarily stop when I replicate that action another time. I've looked at the manuals, but I'm at a loss as to what might do this.

Have I discovered a gremlin I'm just going to have to chase down over time or something those more familiar with Rowe can point me right to?

Thanks all!
Nelson

Hi Nelson,
I'm not quite sure what you consider "backwards" in that tone arm ? Rowe installed the cartridge "backwards" in all tone arms that were located on the left-hand side of the playing record (1100 mech., on up).
Rowe was "in love" with those 3M red connectors, for a number of years-- caution, once "faded to white", they become "crumbly", un-reliable, and IMHO,---- NEED--- to be "replaced".
Since I don't recall if that model has a solenoid in the keyboard, I would investigate that as the source of your "hum"--especially if you hear it when credits are established !
Ron Rich

Glad to know those connectors were factory issue

Yes, he had installed the backwards cartridge backwards. My guess is that it was missing entirely when he got it, bought one, then assumed it went in the typical orientation. I guess he didn't notice the tonearm was on the left side of the turntable!

I think I may have finally located the hum. It seems like it's coming from the solenoid in the sprag assembly. I can also feel a slight vibration when I touch it. I'm going to go through the manual and check to see if it needs adjusting. Since that falls under the maintenance section, I suppose this is something I'll need to keep up with. I see a lot of questions and answers here relating to that piece, so I think it would behoove me to become very familiar with it!

Nelson

I suddenly developed an Error 30, so I followed the optic adjustments in the manual. As soon as I would get it adjusted, I would get that solenoid noise and the error returned.

I pulled the sprag assembly out and found that the 2 of the bushings were missing and the other 2 only existed in pieces. I've seen these bushings being described in various places as rubber, but these pieces appear to be hard plastic. Either way, they're totally destroyed. The teeth on the gear also looked to be caked up with old grease and were a bit worn. I suspect the bushings were still in place when I first began working on this and then self destructed once I got it going. I've ordered the entire wheel and hub assembly to replace this one.

The vibration/hum was definitely coming from the sprag unit, and I now know that the bushings were completely shot. Is this a typical reaction to the bushings or should I count on still having that solenoid problem after I replace those parts?

Thanks,
Nelson

Starting to feel like I'm talking to myself, but here's my latest update

I received the new sprag gear assy and installed it this morning. Definitely solved the problem of the old one being in pieces, but I still have my "hum".

I had thought this was coming from the sprag solenoid since I could feel it vibrating. I found that when I depressed the solenoid by hand and unlocked the sprag, the basket began to turn....very slowly.

I've spent the day checking connections (yes, I have previously soldered all pins on the boards AND removed every wire from every wire from connectors and cleaned, reformed them) and voltages. As the carriage motor runs perfectly I know it's getting full voltage and switching from the mech controller when it should. The problem is a low voltage it's getting when it shouldn't be running. I traced the circuit as best I could without an actual schematic of the mech controller and I'm "pretty sure" it is a leaking triac.

Is there any place to get an actual schematic of this board, or a list of parts that are on it? The numbers on the triac crosses over to nothing I can find. I know, the simple solution is to buy another board or send mine out for repair, but I obviously prefer to do things my way. I just want to do them the right way. Anyone else here go to component level that might be able to provide a good number so I can find this part? I would truly appreciate any information I can get!

Thanks,
Nelson

Nelson,
2N6348--TD 2500 D-- for the Triac--NTE 3047 for the opto coupler. Ron Rich

Thanks very much Ron!

Is this a fairly common issue with these or do you have the schematics for it (or both)? You had those numbers posted pretty quickly

Hi Nelson,
You are welcome !
Well, sorta--it's a common failure of that type of circuit---I do not re-call seeing it in a MCC before, but I must have had some type of problem with that circuit sometime in the past, as I have noted the parts in my (very expensive !!!) " R-90 shop manual".
Ron Rich

Hello Nelson,

I have seen this on a number of occasions and yes when the sprag solenoid is held in the magazine motor turns very slowly.
It is leakage in the magazine motor circuit, check out Z201 & Q203 but my money is on the Z201.

Regards
Alan

Alan Hood
ami-man
UK

Thanks Alan!

I'm working without the benefit of an actual schematic, so my troubleshooting on the board is limited to following the traces. I'm going to be on the lookout for the shop manual, but I was very happy to see that the complexity seems in line with my electronic skills - both stuck in the 80s! Fortunately Ron passed along both of those numbers to me, so I made sure to include both of them when I ordered the parts.

It sure would be nice to NOT have to order every little thing from the internet. Find a problem, order a part, wait for the part then fix the problem. I keep getting closer to having this unit working, but so far each repair has only allowed me to discover the next item that doesn't work, thus resetting the "order and wait" clock!

Nelson

Thanks so much guys! I replaced the triac and opto chip and problem solved!

You're welcome--glad you got it !--Meant to axk you--what are the numbers on the original opto ?--if you still have it--
Ron Rich

The original opto number is GE3010

Nelson

Thanks,
I am almost positive that the 3020's I have, will work along with the H11A1 and H11A2's I also have--
Ron Rich