LDR 144-070 for MC2200/2205

jlovda

jlovda

Things I loved from the 60's and 70's
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Does anyone know the generic replacement for this Power Guard LDR? Newark sells VTL5C9-x LDRs but there are about five "-x" variations. One channel of an amp I am working on will not limit and clips. I will be changing this part and the LM201 comparator to see what happens.

Thanks
 
It is different than the one used in the muting circuits of many of the amps.....I think they are the same ones we use to replace the Clarix devices used in our SoundTeck 1701 distortion analysers.

I will need to check my notes when I get the shop open Monday.
 
Ldr 144-070

Hello !

I think they are the same ones we use to replace the Clarix devices used in our SoundTeck 1701 distortion analysers.

YES !

they are used in 2205/2125/2155/2255/7270/C33/C34V and some other !
 

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Has anyone been able to verify which VTL5C9 to use in the Power Guard circuit?
Thanks
 
Sorry John, forgot to check my notes this morning.

If you still have the c34 around it should have both vactec replacements in it, one pair for muting, another pair for the PG.

My luck was that they were usually installed so you can not read the writing......Murphy you know
 
I know this is a rather old thread but does anyone have the current replacement part manufacturer and part number for the LDRs inthe 2255. One is the Power Guard LDR (McIntosh # 144070) and the other is the Muting LDR (McIntosh part # 144159).

I see that the VACTEC VTL5C9 is mentioned above but I am trying to verify. I wouldn't want to put the wrong part in....

Thanks for your assistance!
 
Matt's Dad said:
I know this is a rather old thread but does anyone have the current replacement part manufacturer and part number for the LDRs inthe 2255. One is the Power Guard LDR (McIntosh # 144070) and the other is the Muting LDR (McIntosh part # 144159).

I see that the VACTEC VTL5C9 is mentioned above but I am trying to verify. I wouldn't want to put the wrong part in....

Thanks for your assistance!
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The following is from my notes:

144-070 = VTL5C2
144-159 = VTL5C9

Verify installation orientation using the schematics and product data sheet.
 
I believe these have been discontinued for a number of years. The major suppliers have been out of stock for a while, although some guitar parts supplies have had some stock.
 
Eh!!! As luck would have it these are obsolete and almost impossible to find. Does anyone have a substitute for either or both of these LDRs?

Thanks for your help!!!
 
I would think, with a DC power supply maybe even a 9 volt battery, and a multimeter, you could test the devices you believe have failed and then confirm their failure.

I have used up my backstock of failed input muting devices so I will need to find a sub or pay for McIntosh investment in backstock, now 40 years old or find a reliable sub myself in the future.
 
I'll check with McIntosh to see if what they have is a NOS Vactec VTL5C2 (144-159) and VTL5C9 (144-070) or if it is a substitute. Will post the results so everyone will know.

I closely inspected the 045864 boards and see that LDR 201 thru 501 are all the same part number. Schematics clearly show that they should be different but they all say: 21L682-9433 on the body of the device. I've looked at the specs for both devices and their operating characteristics are completely different. The difference could be the reason it's not working as it should.

I'm wondering if the folks at McIntosh made an error when they put these things together.
 

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Originally they were two different devices. The first one that Mac engineering found out about failing was in a MC2250 muting circuit In 1982 by me. Intermittant as all get out it was a repack that my boss had purchased. It failed on a night we were hosting Gordon Gow for dinner at his house and his system would not play a channel.

I believe it is time to pull out the questionable device(s) and test. Guessing will not answer your questions.
 
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There were the Clarix models and the Vactec models. I have the Vactec ones. In an earlier post you had mentioned that the bad ones were Clarix.

My one point of concern with the unit I have is that all of the LDRs are the same. There should be two different part numbers and they are not.

So I'm ordering from McIntosh tomorrow. I will see if they have NOS Vactec or some other type of replacements. I should buy a hundred of each and hold them until they are worth $100. a piece... {-;
 
Matt's Dad said:
I'll check with McIntosh to see if what they have is a NOS Vactec VTL5C2 (144-159) and VTL5C9 (144-070) or if it is a substitute. Will post the results so everyone will know.

I closely inspected the 045864 boards and see that LDR 201 thru 501 are all the same part number. Schematics clearly show that they should be different but they all say: 21L682-9433 on the body of the device. I've looked at the specs for both devices and their operating characteristics are completely different. The difference could be the reason it's not working as it should.

I'm wondering if the folks at McIntosh made an error when they put these things together.
Click to expand...

The MC-2255 had a total of three different driver boards throughout it's production run:

Driver board V1: S/N's CT1001-CT2449, V2: S/N's CT2450-CT3263, V3: S/N's CT3264 and above.

My second MC- 2255 had V1 driver boards. It used CLM6000's for the muting & powerguard LDR's.

Without an early service manual it would be difficult to confirm, but I don't believe McIntosh made an error in putting the same LDR in both location on earlier units. I believe there was a revision and they changed to using 2 different devices, most likely on the V2 driver boards. This is just an educated guess based on what I've seen -

#1 2255 - Late production model, V3 Driver Board, CLM6000 & CLM6500 for LDR's
#2 2255 - Early production model, V1 Driver Board. CLM6000 in both locations
MC-2150 - V2 Driver Boards, CLM 6000 & CLM6500's

I have a MC-2250 that I'll have to open up to confirm Driver Board version.
 
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Sometimes you need to just test things yourself......

Found two PerkinElmer Vactec Vactrols VTL5C7 as well as a pulled CLM6500 from a repaired C33.

Nine volt battery confirmed the DEAD CLM6500 and properly functioning VTL5C7.

So the devices can be checked outside of the unit with a simple 9 volt battery.

Tested a second CLM6500. It showed a resistance of 1367 ohms when activated. I believe that is out of spec but I did not measure the current of the 9 volt.
 
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Thanks for the information!!!

I ordered two of the Power Guard LDRs this morning.

The interesting thing is that all of the LDRs (Power Guard & Muting) on the 045864 pre amp cards are the same part number!
 
Does anyone have a picture of an original 045864 Preamp circuit card? Would like to AB it with what i have in my 2255.

Thanks!
 
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