X101B, Hi-FREQ(10KHz) Phono Squeal, Volume Dependent

[arts]

I only brought it up because my own Fisher R200 has been giving me s**tfits because of the same stupid grounding problems. It seems that a lifetime spent in a more humid environment may play a role in this.Although many of the riveted ground-points looked fine visually,giving them a wiggle during operation was very revealing,and indicated that a lot of re-working would be required.The only thing that was stable on this bloody thing was the dial illumination! Luckily,I still have my old Weller D550 (260 watts,take that you "/$%??&!) so I'll be soldering all of these points directly to the chassis.

 

[dsndblm]

Larry,

I had the same issue with my TA-600. The problem ended up being old, corroded RCA jacks.

 

[larryderouin]

Well the squeeeeeeeal is back with a vengeance. I had the Allman Brothers live at A&R studios album on playing and it started all of a sudden.
Controls set as follows.
Volume (1/2way).
Dimension (full stereo)
Treble (3:00)
Bass (12:00)
Balance (centered)

Squeeal is tameable by turning down Treble or Dimension to Center (NORMAL). Any combination of the 2 past 3:00 turns on the squeeal (yeah I know I'm spelling squeal wrong, but this is what it sounds like). Time to break out another turntable and see if that is the problem. Right now I have a PIONEER PL-A45D with a Shure V15-III on it, set to 1.25gr(*). When I change headshells and put the PIONEER PL-30 (3.0gr) on it takes a little bit more control input to get it to squeeal. Speakers are KLH-17 about 4 ft away and in front of the turntable. I haven't done anything to the 101-B as I've had a 400 on the bench since March when Dee went into the hospital. Guess I'll have to light a fire under my ass and get that finished so I'll have room for the 101-B. Batching it is fine, but sometimes you need a frying pan launcher to have around. A dog with separation anxiety doesn't cut it.

(*) I originally had the V15-III @ .75gr and the squeeal would come on sooner, which is leading me to think it may be the turntable/cartridge vs the 101-B. 1.25gr is heaviest I'll set it. The PL-30 is rated for 3.0 to 4.0gr. I don't want to have to bump the weight up to 4.0gr. Both stylus are new.

I'll change turntables, and see what happens.

 

[Tim D]

Hi Larry,

Going to watch your progress as I might have the same issues with my KX-100 (kit form of X-100-B) among several other issues. I'm still in the early stages of my investigation, so I haven't narrowed mine down to only the phono section yet, but my next steps should prove that out.

The fact that your squeal is either on or off hints that it might be a connection problem. The idea of a ground not making contact is a definite possibility. Another possibility is a hidden short somewhere too. The fact that your squeal happens only on the phono might tell you to look between the phono RCA jacks and the inputs of your phono pre-amp tubes.

I'm not an expert and I'm just postulating.....

 

[larryderouin]

Tim; Any input, no matter how inane or insane it sounds to you, helps. Sometimes it's the obvious stuff that is overlooked due to lemming conditioning. Someone comes up with an obviously good solution and everyone piles on. Sometimes it works, sometimes it don't. Then you have the guy who's just learning and he comes up with something out of Left Field and it works. Then every one goes, "Oh yeah, I knew that would work" (this is an exageration but you get the idea. I'm not dissing the other poster's as I'll look into each possible solution).

I'll finish the 400 then tear into the 101-B. I've got some new RCA Jacks and some 1/8" masonite board to make new input boards with. At the same time I'll go over all of the grounds.

If the SL-1200 is quiet on the 101-B, that tells me it's the PIONEER, and not the 101-B. So the 1200 goes on tonight and does a test run.

 

[dcgillespie]

Larry -- both channels, or just one? This is absolutely a shielding problem, but strange you're still having it with the extra shielding installed. And the fact that it started all at once tends to indicate a loose connection. Do you have a close by amp of some sort that can be use to help troubleshoot this sucker?

Dave

 

[larryderouin]

Both channels. I can break out the TX-100 from the shed. What cha got up yer sleeve...??????

 

[dcgillespie]

I hope that will have a high enough input impedance. If so, the plan would be to do this: come straight off the high and low terminals of the volume control in the X-101B, and go straight into the Aux input of the external amplifier. Now, assuming that the X-101B will misbehave when it's volume control is advanced, then the turn it's volume control to minimum (not off, just minimum volume), and now advance the volume of the external amplifier. If it does NOT squeal, then it can only be happening due to feedback occurring within the X-101B itself. If the external amp does squeal, then something within the phono preamp/tone amp/line amp stages is causing it -- rather than the old input close to the output issue within the X-101B itself.

It is strange however that it is in both channels, and that it (apparently) comes and goes. Have all the power supply caps been changed?

Dave

 

[gadget73]

Does this by chance have a single tube that runs both channels at some point? I had an extremely microphonic tube in a console, and it would scream at high volumes just because it was mechanically feeding back.

 

[larryderouin]

All NEW caps, Filter can's, etc. The complete set of 6 12ax7's have been swapped TWICE with kits from the 400's. (one set all Sylvie's, one set good matching section Tele's) Current tubes are Tung-sol's in V2,3,7,8. V1,6 have Sovtek 12ax7LPS. V4,5,9,10 are Tung-Sol 7591 Re-Issues and a IEC Branded Mullard GZ34/5AR4. All the gear is sitting on top the Executive except the KLH's. They are sitting on NLA's flanking the Exec about 1 foot out. Maybe a resonant harmonic thru the turntable??

I pulled the phono plug's from the PL-A45D off the 101-B last night and put the controls as in the 1st post last night. All I got was the normal ungrounded hum/hiss from both phono's. I had the controls maxxed out last night and NADA, Nothing, NOT ANYTHING except the normal background hum/noise. Note that the squeeal isn't really volume dependent but more from the Treble and Dimension control positions when the Turntable is plugged in. But only when volume is more than 11:00. with the treble and or Dimension set to 3:00 or more and it squeeals like a pen full of pigs. Turn one or the other to flat or normal and it stops. So I'm tending to think it's in the turntable. I'll repeat last night with shorting plugs tonight also before trying the other turntables.

I'll break out the SL-1200 and the FISHER standalone(with an ATE)and see what gives.



One more thing. If the Tape/Phono EQ switch is thrown at a normal rate to one or the other position while in Phono or tape positions, it gives off one hell of a squeeeeal about 1/2way in travel. I think this is from feedback going thru both parts of the PEC, while the contacts are touching both sides. Correct??? Anything can do to alleviate this other than don't do this? I find LP's DO sound a lot better in TAPE mode than LP due to the different EQ settings.

 

[Tim D]

Larry,

Are your V1 and V6 (phono preamp) wearing their metal raincoats?

 

[larryderouin]

Yep, so are V2 and V7.

 

[Tim D]

Yep, so are V2 and V7.

I've got a possibly similar problem on my KX-100 that I'm going to start debugging tonight. When I received it some of the wires were disconnected from the selector switch. During the refurb I did a continuity check on the offending switch position and it appeared that the switch was working. I put the wires back on the selector switch, but maybe I need to undo that change and see if that helps. The wiring that was disconnected was for the phono selection, so there might be a pre-existing problem on mine that might point the way to yours too. I'll let you know if I find anything.

 

[larryderouin]

Everything is on HOLD for the next few days. Dorcas was taken to hospital (AGAIN!) @ 3.pm with a 103.4 temp, confusion and belly pains. White count is 16K which is high. So she's being admitted and I have to deal with the Nursing home as far as her stuff there and getting her discharged., the finding out from Medicare and Carefirst if the 100 days in the rehab are accumulative or if it starts all over again after a hospital admission and discharge. Oh the FUN Never ceases!!!

DAMMIT ALL TO 4377. (You guys can imagine how damned frustrated I am right now.) Gimme me a week or two to get everything straightened out.

 

[dcgillespie]

Best wishes with all of that, Larry. When you do get back to it, realize that the EQ switch is selecting to different EQ curves by selecting to different feedback networks. However, when set in-between the two settings, then there is NO feedback, so that the phono section -- which normally has a gain of about 85 or so, now has a gain of nearly 1200 or more! With that kind of gain running around loose inside the chassis, there sure as 4377 will be a lot of feedback squeal then!!

Stiff upper lip --

Dave

 

[larryderouin]

It's the PL-A45D that's causing the problem. I took it out and replaced it with a ZERO 100. 2 different carts (Pickering 500v.3(2.5gr) and a Shure M91(1.5gr) on separate headshells). Played 2 sides of Live at A&R Studio's (Allman Bros.) with Treble full up, Dimension Full stereo, and Volume at about 2:00. Nothing but Duane, and Gregg jamming like only they could do together! NO SQUEEAL! No Hog's, No Piglets, and sure as hell NO SOWS! Just absolutely QUIET between tracks, and Fantastic sounds.

I then Hooked up a SL-1200 (the original Servo model and some say the best sounding of the bunch), and put the Shure V15-iii(1.0) on it(Same cart and headshell I used on the PL-A45D). Same parameter's and tracks as on the Zero 100. No Squeeal, NO Pings, No Snaps, Crackles, Pop's, NOTHING! DEAD SILENT except for that sweet Southern Rock/Blues/Jazz that the Allman Brothers did so well!

The X-101-B performed like a CHAMP. Absolutely no problems with it over the 1.5 hours it took to run this experiment. As the 1200 is now a totally manual deck and absolutely nobody has a tonearm lift for this model (it's different than the MK-II to MK-V) I very seldom use it. Maybe someone on the turntable forum has a mk-I and can make a plaster casting of one. Hmmmmm! I really like it and would love to get more time on it but I'd like to not have to get up every 15 minutes and stand there waiting for the record to end and the stylus get onto dead wax so i can lift it manually.

It's NOT THE X-101-B. I'm gonna try the PL-45D on a couple of PIONEER's from the same era (1974-75). Might have to change the cables.

Larry

 

[Tim D]

Great news Larry!

 

[larryderouin]

I pulled the Tung-Sol 12ax7's and the 12ax7LPS's and installed the Sylvie's in it and did the tests again with the Zero 100 and the SL-1200 today. NO PROBLEMS.

The Sylvie's sound as good or slightly better than the Tele's. I'm going to keep the Tele's in the Early 400, the Tung-Sol's and Sovteks in the Late 400.

 

[gadget73]

Hm, wonder why it acts up with one turntable and not the other. Must be some odd combo of parameters that makes it go batty.

 

[larryderouin]

Slight diameter differences in the Japanese vs US or Briitish connections is what I'm thinking. All of the turntables have their original cables. Plus with the worn out RCA JACKS on the X-101-D and you can get opens or bad connections.