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prt1969
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turntable troubleshooting

Recently having issues with my upgraded Rega P1 turntable. Glass platter and Ortofon OM20 cartridge. For some reason, vinyl now sounds like garbage thru my speakers (Monitor Audio RS6's). Connects into a McIntosh C28 pre-amp, to a MC2105 amp. For a period of time, everything sounded great. Now I am having problems with the stereo mode on the pre-amp; only if I use the L to L & R mode do I hear sound out of both speakers; mono works ok. I've plugged in a digital source into the aux input on the pre-amp and everything works and sounds fine. I've tried both phono1 and phon2 inputs with the TT and same results. I think I've narrowed it down to a problem with the Rega. Bad needle? But that would not explain the stereo mode problem. At one point, the Rega sounded great. Any suggestions/ideas to point me in the right direction? It's driving me nuts.

bertdw
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Re: turntable troubleshooting

Correct me if I'm wrong, but it sounds like your mode switch (L to L & R mode) is sending the left channel to both output channels. This seems to indicate that you are only getting one channel of your turntable through the system. It could be the cartridge, the wiring, or the phono stage of the preamp. Try swapping (reversing) the left and right channels of the turntable at the preamp input, while leaving that mode switch in normal stereo. If the other speaker is now playing, it's the turntable or cartridge (or wiring). If the same channel is out, it's the phono stage in the Mac.

prt1969
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Re: turntable troubleshooting

Sounds logical; I'll give that a shot.
Thanks for the reply.

bertdw
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Re: turntable troubleshooting

You're welcome, anytime. Let us know what happens!

Jan Vigne
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Re: turntable troubleshooting

Unless you've played hockey with the Rega I would suspect a thirty year old pre amp to have problems more than I would a relatively new turntable or cartridge.

As suggested you are placing the "L" signal only in a mono to both channels configuration. Testing the line only inputs isn't telling you anything about the phono section - phono 1 & 2 on the C28 are feeding the same phono pre amp with the provision to play either of two tables or arms.

If you are confused after you do the switching of L&R signals, try connecting just a straight interconnect cable with RCA's at both ends to one of the two phono inputs. With the volume down to a minimum touch each center pin of the L&R RCA. You will very likely hear a slight buzz out of the left channel RCA and nothing from the R channel. If that's the case, the pre amp needs to be serviced.

prt1969
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Re: turntable troubleshooting

More good info; thanks.

I'm still thinking it's the Rega; I bought it used online at AudiogoN, so I don't have a good history of what it has been thru. The MAC C28 pre-amp, MC2105 amp, and MR78 tuner were all serviced last year and brought back to original specs. Unless they did a crap job or something on the pre-amp phono side decided to give out?

Anyway, I think I have enough tips now to zero in on the culprit. Thanks again.

Jan Vigne
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Re: turntable troubleshooting

There's no reason to think anyone did a crap job. Techs do not replace working components unless they show obvious signs of potential failure. Most of the parts inside the phono pre amp can look perfectly fine - even measure well - and still go kaflunk! without warning. No tech could do much in advance of this failure other than ask if you wanted to spend $7-800 or more replacing almost every component inside a thirty year old pre amp. And what they put in probably wouldn't be as good as what Mac originally used.

Just think that after thirty years things break.

Buddha
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Re: turntable troubleshooting

Aloha.

Just to add to the stew:

I have a C28 myself, by the way. Great minds must shop alike!

Both phono inputs go to the same circuitry inside, so there is only one phono section, with two inmputs. So, the fact that the problem persists for both inputs does not exonerate the preamp.

That cartridge should have plentiful output for the preamp.

When was the last time you used the phono section?

The fact that the only way to get L&R sound is to hit the L to L+R button fits the cartridge problem hypothesis, but on that unit, those circuits kick in after the phono output, so you could still get that result from an internal preamp problem.

It may be easiest to reverse the inputs from your table and then see if the problem changes channels, or requires the R to R+L button to make both channels play. If so, then look at the phono set up, and if the problem stays L to L+R, think preamp.

This all makes sense in my head, but apologies if I didn't say it right!

(The fact that CD plays OK also does not acquit the preamp, as the problem may be limited to the phono section!)

Jan Vigne
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Re: turntable troubleshooting

bood-ha!, is there anyone you don't have on "ignore'?

prt1969
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Re: turntable troubleshooting

Duh!! Had a problem with RCA L & R cables being reversed. Not sure how it got this way, but that is another story (can you say wifey, no touchy?). Good tip on lightly tapping the tip of the connectors; pointed me right to the problem. Flipped the connections; everything back to sounding great (to my ears anyway). Stupid post, but I learned a few things.

esander
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new to a Kenwood KD-40R

Hey all, I'm new to having my own turntable so forgive my ignorance (I'm sure there'll be a lot of it).  I just got my Dad's old Kenwood KD-40R from him and it's about 30 years old and has spent many years in the attic.  Here's the problem I'm having.  The music sounds like it's constantly slowing down and speeding up.  It's a magnetic direct drive table so I looked at how the drive was spinning the record.  I took the underside of the table off and removed the bracket holding the drive on.  I turned the table on and the part that the drive turns (not sure of the technical name) had a very interrupted motion.  At the same spot every rotation it looked like that part that turns gets hung up, fights past that spot and speeds back up.  The portion of lag isn't that much, but enough I guess.  My first question is:  turntables should have a smooth, constant rotation and not an interrupted one right?  And second, anybody know how to fix this?  I'd like to get the table working again, for me and well my dad when he tells me he wants it back.  Thanks in advance.

Ed

Bill B
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Yes needs smooth constant rotation

Yes, the essential job of a turntable is to have a very constant, steady, smooth rotation.  So an interruption or a flaw with that is not acceptable.  I have not worked on direct drive turntables so I don't know how to fix this, sorry.  Perhaps some further disassembly and lubrication is needed - by you or by a local technician.  Cost of repair might exceed what you could buy a newer used turntable for.

If you have a very old horse with a broken leg sometimes it's kinder to just shoot it.

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