Marantz 18 receiver needs help

[nickb]

I get about a 4v P-P swing at the driver collectors
The waveform looks much better but gets fuzzy & distorts as I turn up the tone controls
At least there's progress

Did you mean "emitters"? If it really was the collectors of Q7 /Q8 that would be wrong.

You should probe the input the power amp to check for a sensibly sized ( no more than 4Vpp) undistorted signal followed by the output.

Now that you have Q3 removed please measure the voltages again, including the power rails, Now that we have a schematic there is no need to repost it. Just do a table of Q#, pin and it's voltage.

[bigdrums925]

Q3 was already replaced
I can measure all the voltages but would it not be easier to say that I now have a lovely set of equal sine waves on the sockets of the output transistors?
4v P-P on the bases Q11, Q12, and about 15v P-P on the collectors, 0v on the emitters no output transistors installed

Sorry if Im not following advice well. It's just that it will take some time before I can verify everything before reporting back and the nice undistorted waveforms on the sockets
of Q11 & Q12 seem to indicate this left channel should be working as soon as the transistors arrive

Correct me if I'm wrong about that

[nickb]

The problem was you reported the the swing on the driver collectors whereas I was expecting a measurement on the output. The driver collectors is not a place you would normally probe,

OK that sounds about right. There is load on the output due to C30 that is causing the drop across R34 and R29. That will go away once the output transistors are fitted. Turn R26 to maximum resistance before fitting the output transistors to avoid excessive quiescent current.

Time to look at the other channel?

[bigdrums925]

Moving to the right channel here are the measurements in dc volts:
base collector emitter
Q1001 28.5 1.5 29.9
Q1002 46.8 0 47.5
Q1003 .8 -39.7 1.6
Q1004 -38.8 1.8 -39.6
Q1005 .8 -38.9 1.5
Q1006 -38.9 -.2 -39.5
Q2 -.2 0 -.2
Q5 0 0 0
Q6 -.2 -.2 0
Q9 0 42.4 0
Q10 -.2 -42.5 -.2
Q13 42.4 0 43
Q14 -42.5 -.2 -42.7

[nickb]

Looks like Q6 and Q5 may be bad. Remove and retest.

BTW when working on SS amps I always bring the power up slowly with a variac and monitor the current to avoid blowing parts up. I'm not a fan of bulb limiters as they react too slowly to protect transistors in many cases. OTOH a bulb limiter is better than nothing.

[bigdrums925]

I replaced both Q5 & Q6 as they were bad.
But this did not provide for a sine wave on the collectors of Q13 & Q14 like it did for the other channel.
I removed Q10 and checked. Initially it tested ok but then tested bad.
I suspect both Q9 & Q10 are bad and need replacement.
Now, here's the problem. All I know about them is they are a NPN and a PNP device with Marantz numbers and that they are both TO126 case styles.
How can I find suitable replacements since Denon/Marantz are of no help at all?

[bigdrums925]

ANYONE?

[nosaj]

No printing on the transistor is same as schematic 34-1013
716 follows that Marantz # however

i have found some that are hard to read and sometimes a white crayon or even rubbing pencil lead on them will uncover what I'm looking for. I also found this may or maynot help
Marantz Transistor Cross-reference.pdf

nosaj
more detailed info
Marantz-18-Schematics.pdf

[nickb]

I'm waiting for the new set of voltages after removing Q5 & Q6.

PS: Responses are sometimes delayed as email notifications are a bit hit and miss.

[nickb]

I replaced both Q5 & Q6 as they were bad.
But this did not provide for a sine wave on the collectors of Q13 & Q14 like it did for the other channel.
I removed Q10 and checked. Initially it tested ok but then tested bad.
I suspect both Q9 & Q10 are bad and need replacement.
Now, here's the problem. All I know about them is they are a NPN and a PNP device with Marantz numbers and that they are both TO126 case styles.
How can I find suitable replacements since Denon/Marantz are of no help at all?

What is the pin out?
Do they have a heatsink?

For PNP try a KSA1220A, for NPN KSC2690A assuming there is a heatsink and pin out is ECB KSA1220A.pdf

[bigdrums925]

base collector emitter
Q5 0 1 0
Q6 0 -1.7 0
Q9 .4 42.4 .4
Q10 -1.8 -42.5 -.5
Q13 43 .6 43
Q14 -42.5 -.5 - 42.7

Q10 is removed and tests bad at time of these measurements. Also Q11- Q14 are removed
Q6 was replaced with a A844, cant read Q5 but need to double check it is a PNP although the Marantz schematic shows it a NPN
I assume the new drawing you did is correct that it should be PNP like Q6?
Pin outs on Q9 & Q10 are ECB as are the KSA & KSC you recommend.

I will have to order KSA1220A and KSC2690A since I don't have those.
They are both bolted to metal cylinders that are likely heat sinks with insulators, hard to see.

[nickb]

base collector emitter
Q5 0 1 0
Q6 0 -1.7 0
Q9 .4 42.4 .4
Q10 -1.8 -42.5 -.5
Q13 43 .6 43
Q14 -42.5 -.5 - 42.7

Q10 is removed and tests bad at time of these measurements
Q6 was replaced with a A844, cant read Q5 but need to double check it is a PNP although the Marantz schemati8c shows it a NPN
I assume the new drawing you did is correct that it should be PNP?

Q6 is PNP. It is shown wrongly on the Marantz dwg. Q5 ans Q6 are not critical. Not much point in the voltages with missing parts. Things got a bit confused there due to me not getting some responses. Replace the known bad parts first.

[bigdrums925]

So both Q5 & Q6 are now 2sa844's
KSA1220A and KSC2690A came in and I replaced Q10 using a KSA1220a
But this did not bring this side to working condition. So here are a new set of voltages

b c e
Q5 0 .9 0
Q6 0 -1.4 0
Q9 .9 42.4 .5
Q10 -1.4 -42.5 -.5

I haven't changed Q9 yet and very difficult to get to but I suppose that should be next
any other suggestions?

[nickb]

Those voltages are in the ballpark. But.. earlier you asked about Q5/Q6 and I see I got them mixed up. Q5 ( and Q4) should be NPN and Q6 (and Q3) is PNP.

[bigdrums925]

Q5 is a NPN and Q6 is a PNP now.
I don't seem to get a signal through the preamp on the right channel like is present on the left channel.
In fact there seems to be nothing at all signal wise.
Not sure where to look at this point.
Shall I go back and re-measure all the transistor voltages including the preamp?
I haven't removed and checked Q9 but no apparent shorts while in circuit.
But for some reason R42 is burning up after 20 seconds of power up without Q14 or any other outputs installed