Pop when Turning off Power. 2265

[mklein357]

Hello. I just finished a re-cap of my 2265 receiver. Recapped the power supply, power amp boards and the tone board. Also replaced the speaker protection relay and the filter caps. The receiver sounds excellent after the job. Punchier bass, better treble. Just more gooder all the way around. However, there now is a very slight "pop" when turning off the receiver. I don't hear it when turning power on. This problem did not exist before the re-capping. Any suggestions as to how to track down the issue?

Thank-you.

 

[llwhtt]

What did you replace C807 with? If you replaced it with more capacitance that may be your problem.

Craig

 

[Bob]

use a power strip, leave receiver powered on and use strip to power on/off. if no pop
then look at any caps around the power switch and across the AC lines.

replace IF AND ONLY IF you understand AC power - research X, Y rated caps and latest
electrical design rules and laws. do it wrong and you burn your house down AND electrocute
yourself. simply recapping is NOT answer - your receiver is old - perhaps older than you,
and requires expertise. like selling an old house and requiring an update to new building
codes.

 

[mklein357]

All capacitors were replaced with identical capacitance.

I will try the power strip test. Thank-you, Bob. However, I'm looking for advice. You can save the lectures for someone else. As for the comment about burning my house down; seems a bit alarmist, dont' you think? Re-capping isn't the answer? Followers on Audiokarma recommend re-capping constantly. Nothing new there. I have to say that the work I've done on this amplifier has been excellent save for one minor pop in the shutdown. Your second half of your response borders on the insulting. Please refrain from comments on my post in the future.

 

[llwhtt]

Just pull the plug instead of turning it off, if it still pops it's not the power switch/snubber.

Craig

 

[Bob]

ok, then I won't tell you how to do it. I was going to send you a bunch
of x, and y rated caps, for free (see my other posts and offers to others)
and walk you through what to do.

good luck

 

[fernarias]

It's not the caps, obviously.
Anyways, before you do anything set the voltage to 35V, then DC offset to 0 and bias to 13mv. Test unit again.
If it still pops, then a transistor is probably not functioning correctly in the speaker protection circuit. I can't help beyond that since I haven't worked on the 2265 (and my schematic reading ability is slow but steady, I'm an accountant) but the transistor(may be more than one) is probably on P700 and P800. Some one with more knowledge will let you know which transistors to check.

 

[mklein357]

Finally got back around to looking at my receiver. The audio adjustments were all made at completion of my recap and all match the values shown above. Also, pop is not related to the power switch as pop occurs if switching off using power strip switch with amp power left in the on position. Pop does not change in volume with change to volume control. Also, pop sounds to be equal between speakers so it seems like the problem would be located somewhere other than the P800 power amp boards.

 

[KingBubba]

Just turn off your speaker switch before you turn off the power. This will also save a bit of wear and tear on your relay as they will then close with no load on them. The reverse is true also. When turning on, leave the speaker switch off until the protection relay has closed. Turn on and turn off transient are not unusual. The procedure will also protect your speakers from the spikes being generated.

 

[llwhtt]

Does the speaker relay de-energize immediately when you turn the receiver off?

Craig

 

[fernarias]

On the power supply P800, try replacing H805, H806 and H807. H805 should be 2sc945 replace with ksc945, H806 and H807 should be 2sc1313 replace with ksc1815 (from my notes).
There are other transistors on P700 amp that are probably the cause. Of course, you can pull the transistors and check to see if any are leaking (do you have a transistor tester).

 

[mklein357]

Craig, yes the speaker relay does de-energize immediately when shutting down power. I assume it deenergizes a millisecond after the pop occurs. It does seem strange that the transistors might be at fault since the only items I changed out were capacitors and the protection relay. But stranger coincidences have happened. Could it be a ground issue? Thanks for all your help.

 

[mbz]

Others will probably correct me but it seems that at p-off the
protection circuit doesn't discharge fast enough so the relay
contact remains. Two aspects to consider.
- Maybe H806,7 Vb-e "on-voltage" has drifted slightly lower, doubtful.

- C809 (220/10v) does not discharge fast enough. What cap did you replace
it with (manufacturer/series/uf/V). Check state of R814 (lift one leg
and measure). Check solder connections on R814(39k).

 

[mklein357]

Thanks for the advice. I will do the above checks. I replaced C809 with a 220/10 Nichicon part # UKT1A221MED.

But last night another ugly turn of events! I'm relaxing, listening to a record and I notice an intermittent pop from the left channel! crap. Irregular in occurance. I checked voltage at the speaker outputs and the right was holding steady at around 4 millivolts. But the left channel voltage would hold around 4mV but intermittently jump to anywhere from 20 to 200 millivolts. Hard to tell exactly with digital voltmeter. I double-checked voltage at the power supply. 35 volts and steady. Idle current at 13mV on both channels and steady. Where do I go from here? Repair shop? Honestly, a repair shop isn't out of the question, but I would like to attempt this fix myself.

Thank-you for your help.

 

[catrafter]

I am assuming that we are talking about a 2265 NOT a 2265B.
Many times a 'pop' is indicative of a failing transistor in the differential input pair of the power amp, Q701 and Q702. In this receiver, these are usually 2SA722 types and can be replaced by KSA992 'F' suffix parts.
They are circled in white in the picture below.

Tom

 

[mklein357]

OK. Thank you for the advice catrafter. Replaced the Q701 and 702 this weekend with the KSA992 F transistors. No improvement. Voltage still spiking on left channel. Where to next?

 

[catrafter]

If the reference diodes (circled in RED) look like little epoxy gobs, replace each of them with 2 series 1N4448 diodes, like in the picture.
(Q703, Q704). Be sure to observe polarity.
These are also a trouble spot.

Tom

 

[mklein357]

Yes, Q703 and Q704 do look like little epoxy blobs. I can replace. I also read here, http://audiokarma.org/forums/index.php?threads/marantz-2265-p700-amp-board-issue.642628/. That the Q701 and Q702 diodes should be thermally bonded as shown in the picture above. . Mine were not thermally bonded. Is that an important step?

 

[catrafter]

Yes, Q703 and Q704 do look like little epoxy blobs. I can replace. I also read here, http://audiokarma.org/forums/index.php?threads/marantz-2265-p700-amp-board-issue.642628/. That the Q701 and Q702 diodes should be thermally bonded as shown in the picture above. . Mine were not thermally bonded. Is that an important step?

Bonding probably won't affect the 'popping' issue. It is mainly to keep both sides of the differential pair at the same temperature to help minimize drift in the DC offset.

Tom

 

[mklein357]

Thanks. I'll get new diodes on order soon. What's after that? I'd like to order replacement parts to cover a couple scenarios at a time. Price isn't so much a concern since most of these components are dirt cheap. Failing output transistor a possibility?