McIntosh - Hints and Kinks

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I am with Terry. Fast diodes are not a good idea for that application. Put another way. when McIntosh designed the transformer and circuitry, Selenium diodes (rectifiers) were the norm. A slower diode than that would be hard to find. Fast diodes switch hard. Slow diodes switch slowly....just like the AC line.
 
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I was reading the C34v love post by Ron-C and that was one of the first thing he did was put new fast diodes in power supply . I have a C33. Is your suggestion for tube preamps or SS or both ?
 
I was reading the C34v love post by Ron-C and that was one of the first thing he did was put new fast diodes in power supply . I have a C33. Is your suggestion for tube preamps or SS or both ?

Did not Echowars answer this for you already?

It seems that RonC was repairing this part of the preamp, someone had already replaced a single diode and one was burnt. Most likely from a lightning event
 
Yes he did but it was a general explanation I thought ( I forgot about that ) and soft might be a quieter choice . I read a lot posts etc.. and "upgrading" the rectifier diodes is in a lot them . Ron_C was repairing or upgrading he used fast diodes and that was good enough for me . The UF5404 are in now . I'll let you know , thanks for the memory jolt.
 
All is well with my MX110 now!
Went down to Audio Classics on a day trip and Richard Modafferi and the staff (Gary Butt) took care of everything!

I believe it was a cap issue - now LOTS of bass!

(also a wood cab!)

They (AC) are a class act!

Any idea exactly what cap (or caps) was causing this?
 
Any idea exactly what cap (or caps) was causing this?

Not sure...
They were right against the front panel and horizontal...about midway...they were electrolytic and although did not show any evidence of leaking DC with the voltmeter, replacing them both with film caps did the trick...
 
Those are the first caps to replace when doing maintenance on an MX110, 1uF at 150V, a film capacitor is the recommended replacement.
 
MCD7008 - weak RF output

I fixed my MCD7008 player by replacing C213 on the RF amp board. There is no reason to pull the RF amp board. By carefully pulling the body of the cap off thus leaving the two leads I was able to tack solder a new .47uf 63 volt cap in. Now when adjusting the two pots on the board, peak RF occurs in the middle of their range. Prior to the cap change, peak RF occurred near the end of their range. To gain access to the pots, I drilled two 1/4" holes in the plastic frame on the opposite side. I was then able to get a long screwdriver in to adjust the pots. There was nothing touchy at all about the adjustments after the cap change. They have a fairly broad range before playback stops. A proper alignment is recommended.
 
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I fixed my MCD7008 player by replacing C213 on the RF amp board. There is no reason to pull the RF amp board. By carefully pulling the body of the cap off thus leaving the two leads I was able to tack solder a new .47uf 63 volt cap in. Now when adjusting the two pots on the board, peak RF occurs in the middle of their range. Prior to the cap change, peak RF occurred near the end of their range. To gain access to the pots, I drilled two 1/4" holes in the plastic frame on the opposite side. I was then able to get a long screwdriver in to adjust the pots. There was nothing touchy at all about the adjustments after the cap change. They have a fairly broad range before playback stops. A proper alignment is recommended.

Well I'll be...that did it. All lingering issues with my MCD7008 have been solved by swapping that cap. You are a genius my friend! Thank you!
 
Good deal. This is what makes forums so great. The next person will likely find the data and be able to fix an ailing MCD7008 player that has most techs stumped.
 
MR73 repairs

I finally got the MR73 out that I shoved into the closet a few years ago.

The symptom was no audio output.

What I found was an open FM output pot. This is the pot that one adjusts to get 2.5 volts of audio at the output jacks.

The first go around yielded about 30uv sensitivity. Clearly something was wrong in the front end.

What I did to increase the sensitivity to something close to normal was to replace Q1 and Q2 with two 2N5486 JFETs. Now after an alignment the sensitivity is at about 2.5uv. I am going to see if there is something else that can be done to improve the sensitivity further but I doubt anything can be done. The spec is 2.5 uv.

Replacing the festoon lamps with white LEDs made the front panel really look good.

All in all the MR73 is a pretty good tuner. Not great, but good.
 
MC2500 feet

Here are the feet that I used on my MC2500.

31J9HoBph7L._SL500_AA300_.jpg


http://www.amazon.com/Ace-Toilet-Seat-Bumper-24AP/dp/B000H5SMXU

If anyone can find some in black I would appreciate a link.

richard
 
Replacing the festoon lamps with white LEDs made the front panel really look good.

All in all the MR73 is a pretty good tuner. Not great, but good.



I have one of these and enjoy it. Can you describe in more detail or show pictures of what you mean about the lights? Thanks.
 
MC30 Output Tubes

Folks,
I have two MC30s I am rebuilding. All the resistors were out of tolerance and all the paper caps were leaky. These are all changed. Russian PIO caps are in the mail. Figured I would try the Russian caps as these are not very expensive.
I am looking to replace the output tubes but do not want to spend more than $25 each.
I am trying to decide between Tube Doctor, JJ Tesla, Sovtec, Electro Harmonic. I am open to suggestions. Dan
 
I had some spotty experience with JJs, but never had a problem with EH; I actually like them.
 
Ran some original RCA 6L6GCs for a while. Tested 'new', but was not that impressed. Then the Gold Lion KT-66, which was better, and, finally, the Tung-Sol 6L6G coke-bottle. To my ears, the MC30s (like yours, fully recapped and new resistors) did best with the Tung-Sol 6L6G coke-bottles. Tube Depot and others generally sell them for $49.95 per matched pair.
 
MC30 output tubes

Thanks Guys. My second amp came with some old Ge 6L6GC tubes that are medium in strength and sound good but are expensive for two new sets. My friend gave me a couple of Mesa Boogie tubes to try but they were sort of harsh. Dan
 
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