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Marantz 2238 won't power on.

rBuckner said:
Use a coin flip. Q806 is just a rectifier for some lamps or something but it isn't a C945. On the other hand, Q804 is a 2SC945, you should get some Ksc945 just in case. I assume you've done the diode test on it? The 14V zener doesn't need replaced if you can measure 14V at the striped/cathode end under operation. They rarely go bad but with a smoke job you need to check.
Click to expand...

So I think there is a misprint in the parts list in the service manual. The Schematic and the board show Q806 as a C945, and Q804 as a diode. I will attach pictures of what I am looking at.
The physical board matches the top image where Q806 has a C945.

When I lookup Ksc945 on Mouser a whole bunch of Ksc945**** numbers come up. Which one should I get? Does it matter?
 
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It looks like the board layout has swapped Q804 and Q806. There's a "sticky" thread at the forum top with manual errors. Marantz is famous (here at AK) for having many errors as you'll see! Do check for any corrections that may apply to the 2238.

For the KSC945 you want the center lead to be the collector so use 512-KSC945CGBU. It will then install just as shown instead of having to cross the leads. Convenient! Time to order parts!!
 
rBuckner said:
Time to order parts!!
Click to expand...

They are ordered... Now I wait.... While waiting, what is the best way to clean the inside of the unit, there is lots of dust and the unit smells like cigarettes. I have deoxit that I will use on the electrical contacts inside the switches and knobs.
 
So the Mouser order came just in time for the weekend. I replaced the capacitors C802, C803, C804, C807, C808, and C809 with like capacitance and slightly higher voltage.
I replaced Q803 and Q804, and Q806.

I took out and tested Q801 and Q802 and they test ok.

I hooked up to DBT and it passed. I then plugged it in and a few seconds later the relay click.
I still do not have the voltages specified on the P800 schematic.

Things to note on replacing the Electrolytic Capacitors. C809 had a short on the old capacitor. It is now a brand new 1000uF 50V.

When looking at the circuit board I used my flashlight to backlight the board and I can see where it got hot in the past. I will post a picture. It is right at the base of R805, Q805 (zener diode) and Q804.

I pulled the zener diode out and measured resistance. It measures 22 ohms both ways. From my understanding they are supposed to be different depending on the polarity. The service manual calls for Diode BZ-140 14V from another post I see that it can be replaced with 1N5244B. I will have to order this part.

Seeing as the board got hot at one point, I wanted to make sure the trace is not burnt and has additional resistance. I measured from J808 to all the solder points that are connected on that trace and they all have 0ohm resistance. I also removed R805 and tested the resistance. It is right on at 22 ohms.

I will be posting more troubleshooting voltages at different places on the board.
 
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rBuckner said:
Alright, progress!
Click to expand...
I guess so. It seems worse as I get no voltage between J814 and J805 now. I am really getting stumped on this one. The following have been replaced:

Capacitors:
C802 470uF 63V
C803 470uF 63V
C804 100uF 63V
C805 Film 0.047uF 50V
C807 3.3uF 50V
C808 470 uF 35V
C809 1000 uF 50V
I replaced them one at a time and marked the polarity of the old cap and then matched the new cap. It also matches the printed circuit.

Resistors:
One lead of each of the resistors were unsoldered and measured and they are within spec.

Transistors:
Q803: 863-MJE1503G Note: I used a little CPU thermal compound on the heatsink.
Q804: 512-KSC945CGBU Note: that on the SM documentation Q804 and Q806 are swapped on the circuit board image. The physical P800 board is labeled correctly. It is also correct in the schematic.
The two new transistors were tested using EchoWars excellent thread. They both pass. Then I soldered them in place.

Diodes:
Q801 and Q802 tested ok, but I have replaced and no measurable change in their output:
Q801 with MUR1620CTRG
Q802 with MUR1620CTG
Q806 with 1N4007 Note: that on the SM documentation Q804 and Q806 are swapped on the circuit board image. The physical P800 board is labeled correctly. It is also correct in the schematic.
Q805 Zener diode. I have replacement 512-1N5244BTR part on order from mouser, should be here later this week.


Other troubleshooting
To assist troubleshooting, I have unsoldered and pulled the following pins out of the P800 to ensure that there wasn't an issue somewhere else:
J808, J807, J806, J805, J813, J812

No change.

Voltage measurements:
J801 - J802: 40.6 VAC
J808 - J813: 8.25 V
J805 - J814: 0V

Q803 collector pin: 56V this should be 46V according to 8.10 in the service manual.
Every other voltage measurement on the schematic is 0V.

Any ideas on what I could be missing?
Could there be something wrong with the transformer?
 
does r808 have any influence on j808 ?
q804 might be in trouble ...but collector on q803 being is a bit odd if so .
maybe check b to e on q803 to see if its working ..
 
petehall347 said:
does r808 have any influence on j808 ?
q804 might be in trouble ...but collector on q803 being is a bit odd if so .
maybe check b to e on q803 to see if its working ..
Click to expand...

J808-J814: 0V. Turning R808 did nothing to voltage.

Q803: I pulled the MJE1503G to test.
Red on Base, Black on Collector. 0.57V.
Red on Base, Black on Emiter. 0.57V.
All other combinations .OL

I forgot to add, I still get relay click about 2 seconds after power on. Which is a positive sign...
 
i meant to test in circuit powered up but i guess it will be ok anyway ..
if you can get bce voltages for all 8** transistors without blowing anything up it should help see whats happening .. if its too tricky dont bother ..
base of q803 would be good to see the voltage
 
petehall347 said:
i meant to test in circuit powered up but i guess it will be ok anyway ..
if you can get bce voltages for all 8** transistors without blowing anything up it should help see whats happening .. if its too tricky dont bother ..
base of q803 would be good to see the voltage
Click to expand...
Just to be clear. I place the Black lead on J814, and measure using the red probe on BCE for Q803 and Q804? I will be careful not to short out the leads. I have a good probe that has a cover down to the point.
 
yes j814 should be at ground potential .. be worth checking it is as it happens .. simply check voltage from chassis to j814 .it should read damn near on 0v ..
 
petehall347 said:
i meant to test in circuit powered up but i guess it will be ok anyway ..
if you can get bce voltages for all 8** transistors without blowing anything up it should help see whats happening .. if its too tricky dont bother ..
base of q803 would be good to see the voltage
Click to expand...

I just replaced Q804 with a newly tested one from the bag. Here are the voltages.

Q803:
B 0.49V
C 55.5V
E 115mV

Q804:
B 57 mV
C 0.5V
E 0.15V
 
check r803 r804 are at 1.5k .
q803 base needs 35v ish for this supply to be operating .
if they are ok c804 appears to be shorted .. or c805 is shorted but is unusual ..although it can happen .
it is odd you had voltage at j808 earlier though
 
petehall347 said:
check r803 r804 are at 1.5k .
q803 base needs 35v ish for this supply to be operating .
if they are ok c804 appears to be shorted .. or c805 is shorted but is unusual ..although it can happen .
it is odd you had voltage at j808 earlier though
Click to expand...

I pulled C804 and checked that it was not shorted. It appeared ok. I then cleaned up the back of the P800 board with a little rubbing alcohol and q-tips. I also removed solder and resoldered in Q803. I think there may have been a little solder bridge. After powering it back up and testing here is what I get for voltages. A little better but not correct yet.

J805 - J814: 4.28V adjustable up to 5.03V. At least we get something now....

Q803:
B 5.6V
C 52.9V
E 5.03V

Q804:
B 1.2V
C 5.9V
E 0.507V

At this point I am wondering about Q805 (Zener Diode). The one that is in there looks like it may have been replaced before and I have no idea if it was correct. Any idea how I can test it to be sure it is working
 
Here are the latest readings from Q803 and Q804 and compared to spec from the service manual.
Location |Spec | Reading
Q803B | 35.7V | 5.6V
Q803C | 46.0V | 52.5V
Q803E | 35.0V | 5.03V
Q804B | 15.4V | 1.2V
Q804C | 35.7V | 5.9V
Q804E | 14.8V | 0.5V
 
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