alpine mrv 1505

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powers up no output.

where to start? looking from the bottom of the amp with the power cables pointing at your belly....

transistors to the right all the there are first 6
leg 1 - 0.00
leg 2 - 11.8+/-
leg 3 - 11.8+/-

transisitors to the left first 6

leg 1 - 0.00
leg 2 - 11.8+/-
leg 3 - 0.00

transistors 7,8,9,10 both left and right all legs ar between 4 and 6 vdc

tried to post pics... said they were too big... will resize them
 
Try running a ground wire to the RCA shield from the 12 volt ground. This is just a quick test for a regular issue on these where the internal ground reference has been damaged by overload conditions.

If you get sound with the ground wire then you have a damaged ground reference in the protection circuitry that references both the RCAs and the protection to 12 volt grouind.

seen this about 600 times before, very common issue.

Hope this helps:)
 
Re: great info. thanks.

IMPALAMAN1 said:
will try it out. if this is the problem what is the fix?

Well you will need the schematic to tech out the bad ground reference point, so i can't walk you thru that here ( I would hog up too much forum space).

I have seen a simple jumper wire to the ground of the lower rails solve the issue quickly, but there maybe ground loop issues from this sort of repair. If you chose to do this just solder a wire from the 12 volt GROUND, to the ground of the + - 15 volt regulator circuit. This bypass's the original grounding method that Alpine used. The problem will never come back, BUT I make no promises about ground loop noise.
The other solution is to obtain the schematic and tech it out and replace the burnt device in the protection circuitry.

This was caused by abuse to the amp. it has been overdriven to the point that this damaged has occured. The only other possibility is a poor ground for the amp, but that's not what i have seen in the many years these have been around. Oh and by the way all Alpines have this issue, And I do mean ALL Alpines from the Straight and V-12 series. Thay all shared common design in the protection and ground reference area.

Hope this helps:D
 
Perry, pleasure as always

J.O.M.A, tried out your advice, it did and didnt work. so what happend was I powered it up and grounded channel 2 and channel 1. channel 1 kicked on after i pulled the wire away. channel 2 never played. what doesnt make any sense is that the speaker will play on the bridged taps with the channel 1 input only.

the switch for 1+2, stereo, mono doesnt seem to make any difference.


Perry, I will try this tonight.


So at this point im down to the channel 2 output.
 
Re: Perry, pleasure as always

IMPALAMAN1 said:
J.O.M.A, tried out your advice, it did and didnt work. so what happend was I powered it up and grounded channel 2 and channel 1. channel 1 kicked on after i pulled the wire away. channel 2 never played. what doesnt make any sense is that the speaker will play on the bridged taps with the channel 1 input only.

the switch for 1+2, stereo, mono doesnt seem to make any difference.


Perry, I will try this tonight.


So at this point im down to the channel 2 output.

Take a reading of the DC voltage on the rca shield, as referenced to 12 volt ground. I am sure you will find DC voltage on the shield. I have seen as much as 49 volts on the RCA shield. This was caused by a bad insulator under a output FET. The whole case had 49 volts on it:bigeyes: :bigeyes:
These are the typical finds on a amp that looks as pristene as yours does.
As for bad traces (like Perry has suggested) I would look back at the very back end of the board near the 12 volt and protection circuits. I have also seen a blown trace back there in the past.
Good luck:)
 
Pulled the board

and the bottom looks good. not sure what im looking for. but no burnt traces or nada.

here are some pics

im getting an ohm reading off of channel 2 speaker outs that is goofy. with no power the reading is 31 to 160 and keeps climbing and on channel 1 it is 7 and starts climbing

I also get continuity from channel 2 if i touch pos and neg.

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


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


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


i pulled the crossover side and it looked good. i didnt get any pics but it is cleaner than the pw side.


Perry i checked the bus bars and all looks good.

Joma i have not put power to it to check your suggestion. possibly friday.

any other clues?????
 
If you're still dealing with the original problem, you need to determine where the break in the ground is.

Pin 3 of all of the power supply FETs in this amp should be at ground.

Remove power and use your ohm meter to find the break. With the meter set to ohms/continuity/diode check, and the black lead on the ground terminal, follow all connections between pin 3 of the FETs and the chassis ground. If you touch the black lead to the ground terminal (outside the amp) and the red lead to the ground terminal inside the amp, you will read a direct connection (0 ohms/volts depending on the meter's settings).

Continue following the traces and buss bars to the 3rd pin of the FETs (the FETs with 12 volts on the 3rd pin). You will find a break.

Those buss bars cause a lot of problems in amps. Don't trust them. If you find that one has a bad connection, it must be removed. All solder must be removed from it (desoldering braid works best). Then you should clean it to bare copper with fine emory cloth, re-tin it and replace it (after removing all of the old solder from the circuit board). Simply resoldering it is asking for trouble.
 
Re: THANKS FOR THE TALK

IMPALAMAN1 said:
justonemore! thanks for the amp chat... enjoyed the conversation! ill try out what we talked about and get beck to you.



Yeah remember what I said 160 ohms is not a correct reading, just AB from the working channel. Its either the outputs, or the drivers or both. Like we talked about when you dropped by today :) :) :)
 
J.O.M.A

I pulled legs 1 and 3 of the ones with the wierd ohm reading...... they read

(black lead center pin from bottom of board)(ohm) readings are pin 1,lead,3

q211
O.L, 1.2

q213
O.L, O.L

q212
O.L, 1.2

q214
O.L, O.L

(red lead center pin from bottom of board)(ohm) readings are pin 1,lead,3

q211
O.L, O.L

q213
O.L, 2.1

q212
O.L, O.L

q214
O.L, 1.5

opposite side pins 1 and 3 read the same for q111-q114

i think i need to swap the red and black leads on the center leg for the readings to come up... is this refered to as in and out? or as n and p chips?

next..... i checked the center pin and the pads on the board.
q211
131.6, 0.8

q213
136.4, 0.7

q212
131.5, 1.0

q214
136.4, 0.8

so does this mean that the IRF5940 chips are bad on this side. there looks to be a total of 6 per side. per our conversation i should replace all 12.

next the smaller transitors in the middle that you wanted me to check..... they are pretty even with the A/B comparison with hte exception of 1... it is all out of wack....

let me know what you guys think and ill buy some parts.
 
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