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Looking at another APT preamp I have here (very early version), the diodes appear to be correctly oriented. Definitely check for any solder traces and check the power rails to earth in case there is a short

yes, use film for anything less than 3.3uf or 4.7uf if it will fit also, unless the transistors are faulty, there is really no reason to replace them

@mbz yes to OPA2134- a measurable improvement And do replace all the electrolytics

It could be any number of things, however on the assumption(s) that the speakers where the same as usual, the volume was not ear bleeding, and that incoming signal did not have a large surge (pop/click etc), then it likely indicates that there is an underlying potential problem. If this...

The protection circuit kicks in when there is a problem, could it have been the soft clipping indicator?

no problem, I am am wondering whether the problem my be (and forgive me for asking this- but I have also done this myself), self inflicted? I would suggest using a magnifier and bright light to look for track breaks, check the +/- on pins 4 and 8 of each IC, look for small solder links etc.

the black transformer will support the OPA2134

Is your transformer black or covered in a metal case? This would seem to suggest that the popping problem is in the mode stage, between the R>L switching and high filter. The rushing noise problem is likely correlated, and that implies as it rises with volume, that it is part of the gain stage...

also does the tone defeat switch make any difference?

so the problem is from volume control to the output-if you have extra IC's you might try swapping them to see if the noise/popping moves you might consider OPA2134- expensive but very good You mentioned you added some additional bypass caps (what are they?)- I would suggest removing them if...

The rushing noise could be either transistor or IC- though if you have replaced them all that is unlikely. What IC did you use for the volume section? Does the pop occur on the tape outputs or external processor outputs?

I use an RC206- which is 2A, not that the circuit will draw much current

Quite often the service manual says one thing (4.7uf) and what is installed is another thing (10uf). A safe choice is to replace like with like, that is 10uf. Kenwood may have changed the part because of an improvement or because that was what was available at the time and this is not an...

I seem to remember in some Kenwood's, KSC458's should be replaced with KSC1815- there was a post here or on DIYAudio explaining why Did you replace all the caps?

@johnhoef - good to know-enjoy...:)

The 2SA1370/2SC3467 could be replaced with KSA1381/KSC3503 2SA970 = KSA992 and 2SC3423 = KSC2690 probably

From some research of others who have replaced these transistors the following is suggested- NPN- 2N5827/PNP 2N6003/BC550 I have not tried these- but hope this helps,I think many low noise types could be suitable

I have just refurbished another 1130. The IC is used is am LM4562, however I added two 18v zeners to reduce the voltage to the IC to around 17.3v and paralleled them with tow film 0.01uf caps for power supply noise. The unit measured very well and sounds great. As with most of my work, I...

I am wondering if the emitter of X7 is 4.5v?

When researching for another potentially dead motorized volume control, I did find some available try searching for "alps motorized volume control" - digikey and mouser may have some, the are load on EB- the challenge will be finding the right one that fits physically and has the same...

@Rhotundra - you would happen to have a circuit diagram for the BT2 as the balance pot replacement does not seem to have solved my problem

I have a BT2 on the bench at present- working my way through it, dealing with the channel imbalance- so new balance pot going in later this week. @Rhotundra -So will be very interested to measure, test and listen given your comments

So it sounds like cross talk- check that the earth/ground connections are correct. Do you get the same effect from the tape out?

I recently has a couple of KSC1845 test very low Hfe from Mouser

Given that the DBT is showing there is a high current draw, I would suggest removing the output devices and then measuring the voltages on the drivers and work your way back through the circuit. It seems likely that something somewhere is causing that excessive current draw.