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Post by paradisecs on Sept 5, 2018 19:30:15 GMT
I think I had one of those "ah ha" moments troubleshooting a sound issue. I've been studying the schematic looking at the pickup circuit because my USC-2 has good sound coming from A sides of records but the B sides sound horrible; scratchy, garbled, crackles. I swapped needles, changed cartridges, cleaned and re-soldered the tiny wires from the tone arm to the terminal strip. No change.
On the amp the inputs from the needle are blue and red. This is the A & B side inputs correct and they share a common ground? This is where I've been thinking wrong I believe, I always assumed this was left and right channel like a stereo input but that gets converted from input to left and right output somewhere in the amp.
So most likely my problem is not with the mech or input wiring, which I assumed because one side was playing fine but not the other, but in the amp?
I've gone through my manuals and guides but didn't see anything coming right out and saying sound on one side works but not the other so I'm just slow in the head to figure this out.
Stephen
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Post by Ron Rich on Sept 5, 2018 20:41:05 GMT
Hi Stephen,
I don't understand your problem--are you speaking of the 100 side of ONE record, verses the 200 side of that SAME record ?
The input wires are for different channels--the common wire is the grounded for both, at one RCA plug, only. It runs to both terminals at the cartridge. You may, if you wish, jump the two RCA rings together, and test both inputs in the same socket, one at a time.
Which model amplifier is installed in your USC-2 ? Do you have the cover on the output transistors ? Ron Rich
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Post by paradisecs on Sept 5, 2018 21:24:22 GMT
Sorry for the confusion, I'm homeschooling 3 kids at the same time I work on this stuff.
All 100 sides sound fine. All 200 sides sound terrible. It is a TSA10 amp.
First I put in two new needles and got the same result. I then changed the cartridge for one off a unit I know is working fine, and same problem. I've turned the records around, same problem. I stripped the 4 wires from the tone arm and re-soldered them to the terminal strip just to make sure there were no cold solder joints. I'm thinking there is either an issue in the sockets within the tone arm, or it is a problem in the amp.
I think my confusion relates to the # of wires in use when a record is in play. Is it using all four of the wires on the tone arm or is one set for the A side and one set for the B side?
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Post by Ron Rich on Sept 5, 2018 22:15:35 GMT
Stephen,
All four wires are used at all times. From what you are saying, I can only assume that the tone arm position is what is causing your problem. The wires from the cart. "float" under, up and around to the terminal strip. Either they are being caught, on something under there, or pinched somehow when playing a B side. Only one other thing comes to mind--needle pressure -- Which needles are you using, and what is the B side pressure ? --ONCE AGAIN--Which amp is installed, and is the cover on the output transistors ? Ron Rich
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Post by paradisecs on Sept 5, 2018 22:36:06 GMT
Ron,
Yes, the cover is on and as stated above it is a TSA10; code A if that matters. Thanks for the info on the wires, that clears up a lot for me. I couldn't tell if all four were used or not. I'll look in the service manual and your guides tonight to see how to test for that. I have all kinds of pressure gauges for car engines but none for this kind of work.
I was thinking electronic issue, not physical. Just when I feel like I've conquered this machine something else comes up that makes me feel stupid again. Thanks for sharing your knowledge and being patient.
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Post by paradisecs on Sept 11, 2018 21:06:41 GMT
The sound issue turned out to be primarily from a bad spring on the tonearm. Hell of a time getting a spare put in it's place. When the record is loading but before it's clamped down it is hitting the needle. I've damaged two of them before I saw it happen.
I'm going to check all the pickup adjustments but can this be caused by the Transfer arm adjustments as well? Also, when the service manual says to stop on the front of record ###, what does it mean by front?
Stephen
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Post by robnyc on Sept 11, 2018 22:26:02 GMT
Stephen, the adjustment is here: www.flickr.com/photos/90641375@N06/24865555337/ There is one at each end of the sliding cradle. Loosen the Allen screw and slightly turn the hex shaped bolt (red arrow at the left)in the direction that allows the arm to retract. Move only far enough to clear all records. Usually about an 1/8th turn is enough. RobNYC |
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Post by Ron Rich on Sept 12, 2018 3:32:16 GMT
Stephen, Rob,
I dis-agree !
Stephen,
Which "needle" are you using--some aftermarket versions "stuck out" too far-- Unless this phono is one you have just acquired, "adjustment" of the nut should NOT be necessary. Properly OIL/grease, the mechanism, especially the cradle section. Check that it is not binding somewhere when it shifts--play several records on that side, if it "gets better", it is a lubrication issue. If not, see your service manual for adjustment procedures. Which "adjustment number" are you reading that you see the "xxx" ? Ron Rich
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Post by paradisecs on Sept 12, 2018 4:15:14 GMT
Thanks Rob & Ron for the info. This is a USC-2 with the TSA10 in it that has been my learning project. It was trashed when I got it and I have no idea what had been done to it before. I've spent months cleaning it, lubing it, then tinkering with it to learn more. I haven't touched the pickup adjustments as of yet. They seemed a little vague as to what actually they did, at least to my untrained mind.
The needles are all the yellow ones from needles4jukeboxes. I'll check the cradle lubrication again but I've cleaned this thing pretty well and I think I lubed it correctly. I hate to put another new needle in to see it sheered off though.
Service Manual for USC "Transfer Arm 2" - Play Position Clearance says "Scan carriage to the right, stopping it in front of record "179". Clutch 1 says "Scan Carriage to front of "100" record. I've seen the same wording used in several of the adjustments. I'm just not sure what that really means. Clutch 2 says "beyond 100".
Stephen
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Post by Ron Rich on Sept 12, 2018 4:29:21 GMT
Stephen,
On the transfer arm instructions--remove the words "in front of" and add the word "at"--
On clutch 2-- as far as the carriage will move--don't force it--so you can reach "clutch 2 adjusting screw--
Ron Rich
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Post by robnyc on Sept 12, 2018 6:04:18 GMT
Stephen, Rob, I dis-agree ! Stephen, Which "needle" are you using--some aftermarket versions "stuck out" too far-- Unless this phono is one you have just acquired, "adjustment" of the nut should NOT be necessary. Properly OIL/grease, the mechanism, especially the cradle section. Check that it is not binding somewhere when it shifts--play several records on that side, if it "gets better", it is a lubrication issue. If not, see your service manual for adjustment procedures. Which "adjustment number" are you reading that you see the "xxx" ? Ron Rich Ron, it doesn't matter whether it is the styli or tampered arm settings. If it is clobbering the styli, it should be adjusted to clear it. The was a stupid adjustment protocol going around that instructed to adjust the counterweight so that the arm would slide to cutoff if no record was brought up. This in-turn resulted more stupid adjusting to compensate for the fact that the arm would skip at the start of a record. One of the things these idiots did was minimize the clearance between styli and record just before cradle release, that is what may have been done here. The other was to increase the tracking weight. I don't know how idiocy like that takes hold. It goes to show how a lot of people who should have known better, didn't. RobNYC |
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Post by Ron Rich on Sept 12, 2018 13:34:54 GMT
Hi Rob,
Certain after market suppliers of stylli provided a shank on their "yellow/violet replacement needles" that stuck out of the plastic about 1/4 inch. If used in place of the OEM product, the record was somewhat thin, and it "tipped" slightly as it went up the ramp, the record would hit that needle and knock it off/bend the shank, almost every time. Trying to "adjust" for improperly constructed product lead to many problems, as you point out-- I have never heard of "the protocol", you mentioned--must have been an east coast thing ?? Ron Rich
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Post by paradisecs on Sept 13, 2018 22:27:15 GMT
That seems to have done the trick. I don't seem to be able to correlate this to an adjustment in my service manual. Is this one of those field adjustments you just learn about over time? I was looking at "Pick 6 - Pickup Lifting Adjustments" as the possible issue but that seemed to have proper clearance already.
Anyway, thanks for the help Rob and Ron.
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Post by Ron Rich on Sept 13, 2018 22:40:54 GMT
Stephen,
WHAT--"did the trick" ? Ron Rich
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Post by paradisecs on Sept 14, 2018 1:20:29 GMT
Oops, important detail. Rob's adjustment worked great. I checked the pickup assembly and it was clean and moving freely.
Stephen
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