Alpine MRV-1000 repair

[Kei]

Got given it with one channel out with blown FETs and the chassis ground track which i have now replaced. I connected it up to my bench supply to see how it behaved with some power. Set the supply to limit the current and got as far a 4A 4.3V whilst checking voltages. Wasn't sure whether it was a good idea to push the current any higher as i'd rather not blow the FETs, though my bench supply can only go as far as 10A anyway. (wouldn't have expected the amp to require that much for quiescent) Even at this level the repaired side gets warm, whilst the working side remains cold.

Here are the measurements i got if they are of any use:

Repaired channel in red italic (No service manual, so I've numbered them 1 to 4, 1 being closest to the power terminals and 4 being up by the rectifying diodes)

FET 1
Gate - drain 0.01V
Gate - source -4.29V
Source - drain -4.30V

FET 1
Gate - drain 4.24V
Gate - source 0.00V
Source - drain -4.24V

Measuring with ground probe on power ground
FET1/2/3/4 (all measured the same)
Gate 4.30V
Drain 4.31V
Source 0.01V

FET1
Gate 4.24V
Drain 0.03V
Source 4.23V

FET2
Gate 2.20V
Drain 4.25V
Source 0.02V

FET3
Gate 0.02V
Drain 4.25V
Source 0.02V

FET4
Gate 0.02V
Drain 4.25V
Source 0.02V

Switch mode control IC 1 (closest to chassis, reckon this might be the repaired channel, but not certain)
1. 0.02V
2. 0.02V
3. 0.02V
4. 0.02V
5. 0.02V
6. 0.02V
7. 0.02V
8. 2.23V
9. 0.02V
10. 2.20V
11. 2.23V
12. 0.02V
13. 0.02V
14. 0.02V
15. 0.02V
16. 0.02V

Switch mode control IC 2 (further in)
1. 0.02V
2. 0.02V
3. 0.02V
4. 0.02V
5. 0.02V
6. 0.02V
7. 0.02V
8. 2.23V
9. 2.90V
10. 2.91V
11. 2.23V
12. 2.23V
13. 0.02V
14. 0.02V
15. 0.02V
16. 0.02V

 

[Perry Babin]

In the future, use the circuit board designations that are printed on the board (Q809, Q810...).

Confirm that R841-844 are within tolerance.

 

[Kei]

I would use the circuit designations if there were any. My unit has no labels printed on the PCB. If you've got the service manual, I can email you again.

Are these resistors the small (1/8W ?) from each FET as below?

An externally hosted image should be here but it was not working when we last tested it.

 

[Perry Babin]

The circuit board designations may be on the bottom of the board.

 

[Kei]

I've had a look and only the IC's have designations on the underside along with R ch and L ch labels.

 

[Perry Babin]

The resistors that you need to check are the larger ones standing near the power supply FETs. They are 110 ohm resistors.

I'm assuming that you've confirmed that the gate resistors are within tolerance and that none of the FETs are shorted.

 

[Kei]

Not yet checked the gate resistors, assume they should be 100ohms. The FETs i put in tested good. (They were new) The old ones i removed (all 4) were shorted.

 

[Bilawal]

Alpine MRV 1000 circuit diagram required

Hi ,If anyone have Alpine MRV 1000 circuit diagram, plz send me circuit schematic. plz send me if anyone have.

 

[Kei]

Come back to this amp whilst the 3566 is proving troublesome. Tested everything in the iffy channel and all tested good. 4 new IRFZ44's in the psu and it powers up ok, but the current draw is a lowly 0.5A rather than 2.5A as stated in the manual. I've not tried giving it any load as yet but checked the voltages on the 494's and these are the results:

IC801
1. 0.96v
2. 0.96v
3. 3.71v
4. 0.328v
5. 1.58v
6. 5.03v
7. 0.0048v
8. 14.25v
9. 0.16v
10. 0.16v
11. 14.25v
12. 14.25v
13. 5.03v
14. 5.03v
15. 5.03v
16. 0.00v


IC802
1. 0.00v
2. 0.89v
3. 0.08v
4. 0.33v
5. 1.59v
6. 3.81v
7. 0.0047v
8. 14.25v
9. 6.95v
10. 5.40v
11. 14.26v
12. 14.26v
13. 5.03v
14. 5.03v
15. 5.03v
16. 0.00v

Something definitely seems amiss with 802 as pins 9 & 10 are way higher than they should be and pin 3 is way lower.

 

[Perry Babin]

The current draw depends, in part, on the bias setting of the output stage.

Have you adjusted the positive and negative rails to ±49v?

 

[Kei]

Not made any adjustments as yet. I assume they are made by adjusting the small trimpots VR801 & VR802 and measuring the DC between the collectors of two outputs?

 

[Perry Babin]

601 and 602. The instructions are on page 5 of the service manual. If you don't have it, you can get it on the following site:
ElektroTanya | Service manuals and repair tips for electronics experts

 

[Kei]

I've not got a VR601/602 in my copy of the service manual or the one from elekroTanya. 801/802 both have their wipers coming off pin 1 of IC801/802.

Page 5 in my service manual shows the PCB diagram with all of the parts labels. My copy of the MRV-1000 manual is part of the MRV-T300 manual which shows how to set it using TP1 & TP2 where you adjust VR801 to give 52V +/-0.5V across the test points. (obviously this doesn't work with the 1000 as the rail voltages are higher) Test points are across the collectors of the two complementary outputs.

 

[Perry Babin]

Sorry. I read it as MRV-1507.

The rails in the 1000 are ±45v. You can set the voltage between the center legs of the rectifiers to 90v.

 

[Kei]

Tried to adjust the rail voltages today and the right channel (IC801/VR801) will adjust and measured 90V between the centre rectifier legs. (was about 94V pre adjustment) The other channel does not change when I attempted to adjust it. What's odd is when I measure the DC voltage between ground and the collectors of the outputs I get -45V on Q222 & Q226 but only 21V on the collectors of Q220 & Q224.

I've checked the waveforms on both 494's for pins 9 & 10 as well as the drains for the inverters. Scope set to DC coupling and zeroed correctly pre measurement.

IC801 - (left channel) Pin 9

IC801 - Pin 10

Q808 - Drain - Will check others for their voltages but, I believe the waveform shape matched. Time/div had to be adjusted to 5us

IC802 - (Right channel) Pin 9

IC802 - Pin 10

Q809 - Drain - I will check the levels on the others again to be sure but believe they matched. There really is that big an offset.

 

[Perry Babin]

The only thing between the outputs and the rectifiers is the filter inductor. Do you have a bad connection on the inductor?

 

[Kei]

Not as far as I can tell, no.

 

[Perry Babin]

Do you see a 20v+ drop between the rectifier and the collector of the output when measuring the voltage directly between those points?

If you had leaky capacitors, the electrolyte could have eaten through traces, vias...

 

[Kei]

I've not found any leaky capacitors in this amp. I changed the main 3300uF and 470uF parts for new ones anyway. I'll check the voltage between those points. (Centre leg of the rectifier and output collector of corresponding rail)

 

[Kei]

No voltage drop. I see -20.4V on both the centre leg of the rectifier D804 and -the same on the collectors of Q222 & Q226. I see 42.2V on D802 and the same on the collectors of Q224 & Q220.

The other channel appears to shut down as there is virtually no voltage on the rectifiers.