Marantz 2330 Q701/702 (2SA763) replacement

70smidfiguy

Active Member
Hello,

I have a 2330 which had loud intermittent pops on one channel.

I read that the differential pairs (Q701/702) could cause this issue.

I also read that a substitute was the KSC1845.

I purchased those and installed them, however I now seem to have a short on that channel (Relay clicks in if I unplug that amplifier.)

My questions are:

1) Is that the correct tr sub (or is it a KSA992)?

2) If either is a good sub, how do I insure they are matched pairs? (I have a component tester)

3) Why do they need to be "bonded" together?

Many thanks in advance.


20181009_210748.jpg 20181009_210815.jpg
 
Those are supposed to be replaced with KSA992, not KSC1845. 2SA gets replaced with 2SA or KSA. 2SC gets replaced with 2SC or KSC. Put in the right ones and it’ll probably be fine.
 
They are bonded together with a tad of heat sink compound in between the flat surfaces and some shrink tubing because they need to be at the same temperature to do their job.
 
I'm going to double check with you because bonding the 2 992's did not work, I still have a direct short on the amp with those installed.

The original parts taken out for Q701, Q702, Q703 on the P700 amplifier board were "a763's".

The other channel (Which is working) has a "c1845" for Q703 and the other two are heatshrinked so I did not want to take them apart and do NOT know what they are.

The schematic I have shows those three as "2sc1775's"

So now I am a little lost, I could take out the bonded pair for the working channel and try those, but I hate doing that on these amps as the connections between the output tr's and the main board wire wrapping break easy.

Thoughts?
 
After looking at schematics, I think this is different from the typical Marantz power amp. The diff pair is usually originally 2SA722, which is replaced by 2SA992. But as you said, Q701/702 are 2SC1775, and looking around the forum, it looks like people do replace them with 2SC1845. I have rebuilt my 2325, which I thought would be similar to the 2330. It’s not in this respect. I’m no expert, but it looks to me like 2SC1845 is a good substitute for 2SC1775. Same holds true for Q703. Hopefully someone else will chime in.
Steve
 
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I have just done two 2330 restorations in September.

The differential input pairs are NPN and I replaced them with matched and heatshrink bonded KSC1845FTA's.
They are bonded together so that they "thermally track" each other better.
They will certainly not cause your issue if they are not bonded.

I was however having an issue similar to yours with +60vdc on the amp output with the left amp module,which obviously would not allow the protection relay to energize.

It was not a short circuit (as a shorted output transistor)which would cause dbt to light brightly.

I had made up an outboard test harness years ago which made it quite handy for troubleshooting.

Some 2330 amp module have an extra pair of wires that are hard wired to J719/720 which can be disconnected for testing purposes.(They are simply a pair of heatsink over temperature sensors that are wired in series with the relay protection circuit on the P800 board.)

yublsfC.jpg


This unit had previously been "worked on" by another well known audio establishment.

I found some poor solder joints(factory) and touched up all of them.

Put it all back together and finished rest of testing and setting bias,DC offset and +35vdc.
H5nG9LA.jpg



Ready for some run time....

zwvR7vN.jpg




Bob
 
Wow, so much great information, thank you!

Here's what I ended up doing, I found my two original 1775's that I took out, put them back in and replaced Q703 with the 1845 and all was working again.

I cannot explain why the pair of 1845's bonded did not work but I really don't want to keep taking those amp boards apart. Every time I do another wire breaks!

If i still have the popping, I guess I'll have to address it.

Bob, btw, i love the way you extended the interface connectors to test the amp out of the unit, I wish I had done that!

Thanks for your help!
 
Point of order....I am replacing exactly this pair of 2SA763's with matched KSA992F's in a 2240 I am working.

I found this thread whilst verifying the A992 sub so my comments are for posterity.

On the original board they were tied at the emitter as a differential pair would be, but that was it- lot of dead air in between. If you have the same on your board, there is absolutely no need to do any mounting gymnastics to bond them.

Furthermore, the 2240 is DCO settable and your 2330 may be as well - been a few years since I did one and do not recall. If that is the case, matching is 99% of the work. Bonding is a 'eh, if you can you can no big deal' and I repeat this even if the inputs were 2SA798s (or equivalent monolithic device)

I dont expect much thermal issue on the inputs and even if these were driven to nuculah meltdown, its only appx 1/4 watt and in this circuit, you just aint gonna get there unless something else is shorted badly.
 
Point of order....I am replacing exactly this pair of 2SA763's with matched KSA992F's in a 2240 I am working.

I found this thread whilst verifying the A992 sub so my comments are for posterity.

On the original board they were tied at the emitter as a differential pair would be, but that was it- lot of dead air in between. If you have the same on your board, there is absolutely no need to do any mounting gymnastics to bond them.

Furthermore, the 2240 is DCO settable and your 2330 may be as well - been a few years since I did one and do not recall. If that is the case, matching is 99% of the work. Bonding is a 'eh, if you can you can no big deal' and I repeat this even if the inputs were 2SA798s (or equivalent monolithic device)

I dont expect much thermal issue on the inputs and even if these were driven to nuculah meltdown, its only appx 1/4 watt and in this circuit, you just aint gonna get there unless something else is shorted badly.


I Think that I had a lot of Luck.

Years ago I found 12 peaces of 2SA763 in Germany.

It was very expensive ( US$ 10,00 each ) but I fixed my 4400 perfectly.

I'm completly in love with.
 
Hi AK members.
Sorry to use this thread to answer a question:
I need to change the 2sa763 transistors of P700 my marantz 4270.
I don't have the sa992 in my hands.
Can I use sa1015 as a replacement for sa763 on the P700 board?
Thank you for your help.
 
Hi AK members.
Sorry to use this thread to answer a question:
I need to change the 2sa763 transistors of P700 my marantz 4270.
I don't have the sa992 in my hands.
Can I use sa1015 as a replacement for sa763 on the P700 board?
Thank you for your help.
It looks like that should work. A bit less gain, but probably OK. Just make sure pin out is the same.
2SA763 - Vce-->30V, Ic--> 50mA, fT-->60MHz, hFE-->MIN. 250
KSA1015 - Vce-->50V, Ic-->150mA fT-->80MHz, hFE-->120-240 (Y gain code)
 
If this were my unit, I would install the 1015's to try and get it running, but I would be trying to obtain some 992's to go back and replace when you get them. They are the tried and true at this location.
 
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