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Found an exact replacement for the LDR in Mc2255 and other Mac's

cardoctordav

cardoctordav

Member
The original LDR in my MC2255 is part number CLM6500. This part has been discontinued by the manufacturer.

Digikey has an EXACT replacement! Part number NSL28. All of the specifications match the data sheet 100%!
 
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Hello cardoctordav

I am sorry but you are not well informed and not a MCINTOSH specialist and writing a title like " Found an exact replacement for LDR in MC2255 and other Mac's " will captive look from novice who don't know anything about these LDR is this is not the true

Any teached tech working on MCINTOSH know that these 30/40 years old photocoupler (original MCINTOSH part number 144-159 for the CLM6500) is replaced by 144-179 Vactrol VTL5C-9

They are obsolete at the factory , yes , I know but there is many places where you can buy some without problem

Giving today a reference of a very old part is no more usable if you already have the perfect sub given by the factory itself

You can buy the substitute that you have found but in SOUND TECHNOLOGIES units with defect LDR but not in a MC INTOSH
 
cardoctordav said:
The original LDR in my MC2255 is part number CLM6500. This part has been discontinued by the manufacturer.

Digikey has an EXACT replacement! Part number NSL28. All of the specifications match the data sheet 100%!
Click to expand...

Yes, that does look like a very close (perhaps even exact) match. And not just the basic characteristics; the rise and decay times are virtually identical. Any empirical experience yet? After all, proof of the pudding is in the eating;)
 
Does the OP know what value dropping resistor needs to be in series with the LED? The originals are incandescent, correct?
 
Just replaced the dead one tonight and it’s perfect. I let it burn in fir a couple of hours and then replaced the remaining three!
 
clinic-audio said:
Hello cardoctordav

I am sorry but you are not well informed and not a MCINTOSH specialist and writing a title like " Found an exact replacement for LDR in MC2255 and other Mac's " will captive look from novice who don't know anything about these LDR is this is not the true

Any teached tech working on MCINTOSH know that these 30/40 years old photocoupler (original MCINTOSH part number 144-159 for the CLM6500) is replaced by 144-179 Vactrol VTL5C-9

They are obsolete at the factory , yes , I know but there is many places where you can buy some without problem

Giving today a reference of a very old part is no more usable if you already have the perfect sub given by the factory itself

You can buy the substitute that you have found but in SOUND TECHNOLOGIES units with defect LDR but not in a MC INTOSH
Click to expand...
.



this is not a substitute! It’s an exact replacement according to every specification I the data sheet. BTW that is one of the reasons for publishing a data sheet. I have three amps that need these LDR’s and Mac is getting 20.00 each for Chinese made. I actually bought one, didn’t use it. The LDR’s I suggested here are exact in every way and work perfectly. I pride myself on being a diagnostician, not a parts changer. I do my homework regarding replacement of obsolete parts. It seems from my research that the LDR’s McIntosh is selling are obsolete too! None of the big supply houses, such as Digikey or Allied have them available. I did buy some from a questionable source. I won’t use them!
 
Cardoctordav: Did these hold up since you replaced them? I have a new to me 2255 and it appears to be working perfectly (I am in the process of nulling out a right sticky meter, I may be on the home stretch of that as I post-hopefully at least), but I'm reading that I may need to have backups on hand for my 2155 and this 2255. Do they all use the same LDR? How many total? TIA...
 
FWIW, I have an MC2250 that came with a bad LDR, Same amp sans meters.

I tracked down a replacement for the replacement at the time and it works, I forget what it was.

The part in the OP has exact specs as the original so this is a great find.
 
How many would I need per channel? (Or ostensibly X2 for the entire amplifier?)
I presume we're talking about the Advanced Photonix NSL-28 photocoupler, correct?

Here's the link, btw...

https://www.digikey.com/en/products/detail/NSL-28/NSL-28-ND/5039802?itemSeq=381424716

Here's MY count-BUT the schematic overlooks LDR 501 on its parts list. I see it on the schematic, but not at the same place or in the same configuration as the Left Channel list that precedes it. It's there on the schematic itself, just not on the parts list or physical representation section.

Headphone/Preamp: LC LDR 201 (CLM6000)
RC LDR 301 (CLM6000)

Power Output PowerGuard: LC LDR401 (CLM6500)
RC LDR501 (CLM6500)

Are the first two interchangeable/the same component as the second two?

Thanks.
 
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clinic-audio said:
Hello cardoctordav

I am sorry but you are not well informed and not a MCINTOSH specialist and writing a title like " Found an exact replacement for LDR in MC2255 and other Mac's " will captive look from novice who don't know anything about these LDR is this is not the true

Any teached tech working on MCINTOSH know that these 30/40 years old photocoupler (original MCINTOSH part number 144-159 for the CLM6500) is replaced by 144-179 Vactrol VTL5C-9

They are obsolete at the factory , yes , I know but there is many places where you can buy some without problem

Giving today a reference of a very old part is no more usable if you already have the perfect sub given by the factory itself

You can buy the substitute that you have found but in SOUND TECHNOLOGIES units with defect LDR but not in a MC INTOSH
Click to expand...

The specs for the Vactrol VTL5C-9 are not exact.

ARE YOU a well informed MCINTOSH specialist?
 
Clinic-Audio: Just a reminder-I'm still waiting for a quote for 2155 and 2255 lightboxes when you get them ready. (I've solved the 2255 Power Switch issue, so you don't have to get back to me on that.) Just sayin', thx... : - )
 
I see that there are four in each of my amps.
LDR201, LDR301 (CLM6000-old item number #144159)

and LDR401, LDR501 (CLM6500-also old Mac item number 144159)

That's a total of EIGHT of these rascals.

I just spoke with Brian and they're running about $50.00 bucks a pop right now.

Just as a PSA-the NEW Mac Item Number (for the LED replacement version) is 144179.

So...what's the likelihood that they're ACTUALLY going to fail, anyway?

TIA for any advice. That's a lot of cabbage for eight photocouplers...
 
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Ricktptman said:
I see that there are four in each of my amps.
LDR201, LDR301 (CLM6000-old item number #144159)

and LDR401, LDR501 (CLM6500-also old Mac item number 144159)

That's a total of EIGHT of these rascals.

I just spoke with Brian and they're running about $50.00 bucks a pop right now.

Just as a PSA-the NEW Mac Item Number (for the LED replacement version) is 144179.

So...what's the likelihood that they're ACTUALLY going to fail, anyway?

TIA for any advice. That's a lot of cabbage for eight photocouplers...
Click to expand...
The link posted from digikey shows them at $12
 
Thanks, Jimbo40. They'll be here tomorrow. Peace of mind, I guess. I'll pack them away for an ostensible rainy day.

I was waiting to post until I got a pretty good read on the issue that precipitated my inquiry in the first place: The right meter sticking issue.

It turns out it wasn't sticking at all. It was an entire ribbon connector terminal that had developed CSJ's. I've been running it off and on (to test for thermal issue reliability) and it's rock-solid now. The ballistics match the Left channel better, so I'm feeling better about it.
It was the "last" thing in my restoration that was being obstinate. Now I can just relax and listen. Thanks to everyone who responded. The issue's solved just in time for those meters to throw off some of the "100% dark, 90% of the time" time change gloom, lol...
Take care and keep swingin', everybody...
 
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Hi, I'm wondering what the symptoms are of a failing LDR? My MC2255 has a small, random, turn-on pop noises, and I am thinking it might be the LDR's, since I believe the dark resistance decreases over time, from what I have read.
 
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I can confirm that the NSL-28 works well for the LDR in the power guard circuit in MA6200. At approx. rated power, the waveform has just a bit of flattening on the top and bottom and the aptitude remains constant as volume is increased.

Thank you for posting.
 
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