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McIntosh - Hints and Kinks

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12AX7 to 5751 in my MC225

I read an artical about using 5751 insted of 12AX7. I asked my tech guy if it would be safe to put a 5751 into my MC225 and he said it would be fine. So I tried it last night. All I can say is Wow what an increadable improvement in sound. Clairity and stereo imaging. What I used was an GE 5751JG Black Plate.

Gary
 
MAC 1900 FM Muting only Mono

Hi, I received a 1900 MAC cheap. Actually, everything works, FM stereo also works very well but when I turned on the FM muting is I receive only mono not stereo, which is actually normal?

Greets
walo
 
OK, thank you Terry,
but odd, the noise reduction works with activated muting but without stereo.
If another owner might have had from the MAC in 1900, the same problems and could fix it? The service manual and a little knowledge of electronics is present with me.
I have the Mac bought in 1900 second hand and had the transistor Q502 in the SM change because the previous owner had installed an incorrect stereo lamp (6 volts instead of 37 volts), this was not a stereo ad possible, but now it's all back only when the Muting is activated, I have no stereo signal anymore.
Excuse me please my bad English, it is translated with Google, I myself live in Switzerland, my language is typically German.
Greetings
walo
 
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C120, C136, and Q101 can cause loss of stereo when muting, C120 can also cause loss of separation. It is a good idea to replace all of the tear drop tantalum capacitors.
 
OK, thank you Terry,
I'm going to get the parts and replace then I hope that the MAC in 1900 and running again properly.

Thanks again and greetings from Switzerland
walo
 
MC30 rebuild hint?

I am rebuilding an MC30 and just ordered the needed parts. It seems each member has their own preference for parts which to me makes it very interesting . I sat down today and looked at the parts I ordered and compared them to the schematic that I found here at AK. Now I am no expert by any means but I think I could have saved a couple bucks by purchasing a less expensive C2 capacitor. The reason I say this is that it appears this cap is part of the multi connection preamp input which I dont intend to use. I will be using the rca input . What do you think?
 
If the 30 is never going to be used with a C8 or the screw terminal input the cap can be deleted.
 
Looking for a source, or an equivelant replacement for the indicator lamps on my XR14 speakers. Any help is greatly appreciated.
 
I think they are just a grain of wheat style. You will have to pull one and match it up. They light so occasionally can't say I have ever seen one fail.
 
MAC 1900 FM Muting only Mono

Hello Terry,
I first C120 and C136 changed to no avail, now I have I get a type BC148C transistor Q101 and also changed. Unfortunately I still have no stereo with FM-Muting.
What else can it be?:saywhat:

Greets
walo
 
I'm bidding on a Stereotech 1200, in the lead as we speak. Any tweaks exclusive to that item I need to know about?
 
ajamesb said:
Looking for a source, or an equivelant replacement for the indicator lamps on my XR14 speakers. Any help is greatly appreciated.
Click to expand...

Have a pair of 14s gutted on my test stand for binding post and crossover upgrades. Pushed the yellow light from the inside out and saw no part number markings only mil spec wire grade #s
 
The both VU in fullscale once The power turns ON

Hi Terry,
The both VU of my MC2125 in fullscale once the power is turned On.
I swapped this meter pc board 044-624 with the same 044-624 from my first MC2125 and works well.Which electronic parts in meter pc board 044-624 are mulfunction/should be replace?Why too many flaws inside the Glass face of my both MC2125,What kind of preventive maintenance should do to minimize this flaws as I live in tropical climate?My MC2125 usually works the whole day,How many hours was The MC2125 tested in Mac's factory?Thanks in advance.Rgds.Rudi.

____________________
2XMC2125,flawless face plate C28,MQ101,MC2300 amps ads L2030
 
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The both VU in fullscale once The power turns ON

Hi Terry,
The both VU of my MC2125 in fullscale once the power is turned On.
I swapped this meter pc board 044-624 with the same 044-624 from my first MC2125 and works well.Which electronic parts in meter pc board 044-624 are mulfunction/should be replace?Why too many flaws inside the Glass face of my both MC2125,What kind of preventive maintenance should do to minimize this flaws as I live in tropical climate?Thanks in advance.Rgds.Rudi.
 
ROE brown capacitors

Watch for the ROE capacitors used in many 70's models, C32, MAC4100, and many others, if you see them and they look like this, replace them or have them replaced !! Not all of the ROE capacitors will fail but why take a chance.
 

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MX134 lights

I tried to use the external inputs on my MX134. Instead of sound the lights in the front panel went out.
Any ideas?
 
Pull the plug, wait a minute, then try again with the external inputs disconnected. May have to do a master reset.
 
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