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best SUB for 132-070

calman46

calman46

AK Subscriber
Subscriber
I have a bad 132-070 on my recapped MC2502 . It fails E +>C- diode test .just one way only
The McIntosh replacement book lists 2N5303. I found MJ15003 on AK . The other part of the pairs is 132024 Q19,Q20 and 132023 Q17,Q18. I looked at the data sheets and Mj15003 looks to be the better choice, but will they work with 132024/132023 ? The amp plays now with a slightly distorted right channel . I would change all 4, 132-070 . I think the out transistor just crap out do to age. So would 4 MJ15003 work ? thanks
 
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calman46 said:
I have a bad 132-070 on my recapped MC2502 . It fails E +>C- diode test .just one way only
The McIntosh replacement book lists 2N5303. I found MJ15003 on AK . The other part of the pairs is 132024 Q19,Q20 and 132023 Q17,Q18. I looked at the data sheets and Mj15003 looks to be the better choice, but will they work with 132024/132023 ? The amp plays now with a slightly distorted right channel . I would change all 4, 132-070 . I think the out transistor just crap out do to age. So would 4 MJ15003 work ? thanks
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Output transistors right? I just used MJ15024 in and MC250....MJ15003 will work...The 15024 are 250V 16amp, the 15003 is 140V 20amp both are 250watt dissipation...

Both these devices are well beyond the required specs for the amplifier and will work well...

Yes they will work with the existing driver transistors Q17,18,19,20....
 
MJ15003s have been the sub since the 80s...replace them all. It is a MC2505 right or is it a MC2100?
 
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Its A MC2505 . Are there subs 123023/123024 ? The ones listed on AK are N/A .while I'm ordering
 
Output subs are Onsemi MJ15003...TO3 case. Smaller case TO66 style is a whole other matter. If there are a mix of NPN and PNP in the outputs you have a real mess.
 
I have an original configuration , Q17- 132023, Q21-132-070 / Q19- 132024 , Q23- 132-070. Thats one channel .Yes the smaller TO66 are NPN/ PNP
 
calman46 said:
these might work for the TO66 NTE38/NTE175
Click to expand...

As far as keeping it stock, they look like they could work......Although I dont have great faith personally with NTE products, but thats my opinion....

Im sure the human encyclopedia of Mac cross references will be along shortly...
 
kevzep said:
Output transistors right? I just used MJ15024 in and MC250.....
Click to expand...

For me, this is right on. The MJ15024 was the transistor that Mc used in later years (think Mc150) , and is a direct replacement. The MJ15024 sounds better, less 'gainy' and the ones I have gotten are better quality. I would go with the 024.
 
I resemble that statement.....

A year or so ago I posted the experimental parts I used in 1/2 my prodical MC2505...a couple weks ago someone else posted that they had replicated the effort with good results.

I believe trying to peicemeal these amps back togather with all these obsolete parts is surely a deadend.
 
The Mj15024 are in and the amp and MX114 are playing. I am getting some hum maybe ground loop . I have to go back in the MX114 with deoxit . I am getting some static on one side of the new McIntosh volume pot and that's a sealed pot . It happens when I turn the pot real quick .Whats with that ? All and all in these tests (FM and CD) the amp/pre sound very good through a pair on JBL Century L100 new L pads and recapped . From where I was listening the imaging was dead on .It was like there was a third speaker I need the humidity to break here in MA so I can finish this up .
 
Is the hum still in the amplifier when the gains are turned down and nothing plugged into the inputs?
 
CountD said:
For me, this is right on. The MJ15024 was the transistor that Mc used in later years (think Mc150) , and is a direct replacement. The MJ15024 sounds better, less 'gainy' and the ones I have gotten are better quality. I would go with the 024.
Click to expand...

As drivers ...yes...in this case less gain is safer to jump into experimentation than higher gain. The topology of the later amps and the 6.5 ohm autoformer load made use of the 150024/25 devices.

The MJ15003 has been the correct sub since the 80s for the 070.
 
I get that hum with just the amp and no inputs gain full on, buts that normal I thought. Its when I connect the MX114 .
The amp plays loud through the L100's .Half volume is as far as I have gone. The 024's sound really good but are the 0003 safer ? I don't want that grainy sound either . 024 or 003 ? I have both.
 
I looked all over my test gear and saw no setting to measure "gaininess" or "graininess".

According to my 90s semi conductor data sheets the 132-208 (MJ15003) is the replacement.....others here have posted that is what Mac sends as replacements also.

As a responsible repair person I try to stay within the boundries of what the manufacturer suggests...knowing full well we all will have to find newer replacements as semi conductor manufacturers discontinue devices.

Experiment, but say it is an experiment, so amatuers know what they might be getting themselves into.

I currently have 4 amps (and 2 CD players) running different experimental parts and topologies...only one of which has been fully posted, the MC2505.
 
When restored correctly these amps do not hum....much. I can not follow your posts..what parts have you replaced? Have you rebuilt the multicaps? Have you stress tested the main filter caps? Is the hum 60 Hz (ground loop) or 120 and 240 Hz the fundemental and 2nd of the power supply here in the states?
 
I have replaced all the elctrolyics in the MC2505 , with new big caps from Mcintosh . The hum is more when the MX114 is connected ,which has been recapped also. The amp alone will hum when the gain controls are full on and no input source ,which sounds normal to me. I need to it play more to pin point what is going on.
 
calman46 said:
I get that hum with just the amp and no inputs gain full on, buts that normal I thought. Its when I connect the MX114 .
The amp plays loud through the L100's .Half volume is as far as I have gone. The 024's sound really good but are the 0003 safer ? I don't want that grainy sound either . 024 or 003 ? I have both.
Click to expand...

I dont know where you are getting this information from, but I have never heard of output transistors affecting the sound of an amplifier in that way.....
The output transistors have the least effect on the sound in an amplifier....
I've certainly never heard of this "grainy" effect you are talking about....
Sounds like an "old wives tale" to me........
I doubt very much whether you could tell the difference between the two.....

calman46 said:
I have replaced all the elctrolyics in the MC2505 , with new big caps from Mcintosh . The hum is more when the MX114 is connected ,which has been recapped also. The amp alone will hum when the gain controls are full on and no input source ,which sounds normal to me. I need to it play more to pin point what is going on.
Click to expand...

In my experience it appears the MJ15024 are safe to use, I simply used them in the MC250 because that is what I have in stock for servicing my Crown Macrotechs.....
However, the MJ15003 is the correct replacement and since they are available that is what I would use if I was you.....
Sure, use the 024's but you need to be able to watch the amp on a scope for oscillations and instability, you need to know what you are looking for... There is always risks associated with going away from the suggested replacements which is fine if you know what the risks are and how to monitor them..
The critical difference between the two devices .....
MJ15003 ft=2mhz, gain hfe min=25, DC gain hfe = 150
MJ15024 ft=4mhz, gain hfe min=15, DC gain hfe = 60

It seems in these early designs McIntosh went for low bandwith low gain devices in the output section, I am assuming for stability and reliability and probably because there wasnt much else around at the time.....
 
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calman46 said:
I have replaced all the elctrolyics in the MC2505 , with new big caps from Mcintosh . The hum is more when the MX114 is connected ,which has been recapped also. The amp alone will hum when the gain controls are full on and no input source ,which sounds normal to me. I need to it play more to pin point what is going on.
Click to expand...

The amp shouldnt hum, not enough for you to think something is wrong at least.....

Does the hum go away when the gains are turned down?
 
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