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Marantz 2330 Rebuild

As stated. Going slowly on this one.
P800 Board Done (for good this time I hope)
  • As others have noted, the 1/4 pins on the OMRON MY2 02 24V DC relay are removed, and the remaining 6 pins slide right in.
  • Added in extra transistor replacements based on feedback here.
  • I also ended up putting in the wirewound resistor at R801 for increased airflow as @Leestereo had indicated on his fantastic 2325 restoration writeup.

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Back to this 2330 after restoring a smaller Sansui AU222.
I thought I was done with this right channel AMP board. I decided to check resistors before moving on, and found 6 large ones with values way off.
The 4 wirewound 0.27OHM 5W were all reading 0.4-0.5OHM.
The R740 2.2OHM was reading 0.1 OHM or wide open
So more parts to order.


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Leestereo said:
If you are measuring the resistors while they are still on the board you will get erroneous readings. De-solder one resistor leg or remove the resistor completely to measure.
Click to expand...

Thanks @Leestereo ! Is the case only with some kinds of resistors or circuits?

Because most are measuring exactly to spec when measured on board. I thought I read that caps had to be removed to measure, but resistors were ok.

Edit: The 4 large white wirewounds- two settled down to 0.3 OHM, don't have extra decimal place on that low. Two were at 0.5ohm, so similar to on board.

The 2.2OHM that was reading 0.1OHM, reads 2.3 when taken out.

Thanks again Lee. To further clarify, is it only an issue with extremely low resistances like these or is it also circuit dependent? Seems it would be both?
 
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Here's something to think about. If you measure across the leads of a resistor installed in a circuit and the reading is higher than what is marked on the resistor (plus any tolerance) then the resistor must be bad (or out of toleance). It could read lower as there may be a parallel path created by the circuitry it is connected to. (Kirchoff's Law)
When I suspect a 'bad resistor' I make sure of my Ohm meter reading with the test leads shorted together and then measure the suspected resistors in circuit (power of, of course!). If I notice anything much higher than the resistor marking, further investigation is in order.

Tom
 
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Then there is maybe an "offset" in your meter. Short the test leads together. Ideally you'd get zero but I bet you will see 0.1 or 0.2 ohms. Subtract that from your measurement and the resistors are really fine.
 
rBuckner said:
Then there is maybe an "offset" in your meter. Short the test leads together. Ideally you'd get zero but I bet you will see 0.1 or 0.2 ohms. Subtract that from your measurement and the resistors are really fine.
Click to expand...
I did see that leads shorted read 0.1 OHM.
The 0.5 - 0.1 = 0.4, which even if at 0.36 and rounding up, are out of tolerance for 0.27.

To get around that lack of precision, and make inferences about the next decimal, I hooked the two that read 0.5OHM in series, and they read 1.1 OHM, so they really are > 0.5OHM each, and at 0.5OHM if I were to subtract the 0.1.
 
catrafter said:
Here's something to think about. If you measure across the leads of a resistor installed in a circuit and the reading is higher than what is marked on the resistor (plus any tolerance) then the resistor must be bad (or out of toleance. It could read lower as there may be a parallel path created by the circuitry it is connected to. (Kirchoff's Law)
When I suspect a 'bad resistor' I make sure of my Ohm meter reading with the test leads shorted together and then measure the suspected resistors in circuit (power of, of course!). If I notice anything much higher than the resistor marking, further investigation is in order.

Tom
Click to expand...
This makes sense after I went and refreshed my knowledge on resistors in series and parallel. Thanks Tom!
 
catrafter said:
When I suspect a 'bad resistor' I make sure of my Ohm meter reading with the test leads shorted together and then measure the suspected resistors in circuit (power of, of course!). If I notice anything much higher than the resistor marking, further investigation is in order. Tom
Click to expand...
Tom, did you mean to say this? You measure the resistors Ohmic value with the receiver powered up? Or did you mean to say
NO POWER? or power off? I think either of the latter. Had on the wrong glasses and was reading akadrhouse qouting you.

We can measure the voltage drop the of the resistor with the power applied.
We can measure the Ohmic value (resistance) of the resistor with NO POWER applied.

False alarm, go back to normal again.
 
@ akadrhouse, I just have to give you many kudo's for they way you lay out what you are doing
in your pictures that you post!

Very nice and very well done!
 
@ akadrhouse, There are lots of good helpful things that Ak's do that are good and/or great
and helpful. Now that I've started working on my little girls Marantz 2230, it's just plain good.

You are most welcome.
 
I finished up the right amp board(p700). The 0.27OHM 5W were indeed out of spec. All but one were nearly double the rated resistance.
The others marked with blue were indeed right in spec after measuring removed from the circuit, so I left them.

I replaced the main filter caps with 18,000uf/80V. I loved how easy were to screw in with the existing plates and connectors.


Sounds great. But left channel is softer and odd. Getting to it next.

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I think I found my problem in left channel.
The board is in bad shape with some rusted lifted off traces. Look next to my thumb 1/2 inch down and right.

Not sure the best way to fix this.

Can I just solder a solid-core tinned wire ( I think its 22ga) between the two points I've draw a red line between?
There is also a second one above my thumb i need to repair.

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