punch 55.2 dc on outputs, no sound

manninen · 2017-02-26 4:27 pm

nigelwright7557 · 2017-02-26 4:31 pm

I would look first at output transistors.
If they are gone they can sometimes take out driver components too.

Perry Babin · 2017-02-26 7:13 pm

Set the crossover cards to full range. Does that make a difference?

manninen · 2017-02-26 7:25 pm

it was on the high pass when i got it, set it to full range and yes theres still DC on outputs and no sound.

any other measurement what i can do with multimeter?

Perry Babin · 2017-02-26 7:49 pm

Do you have ±15v on the power supply pins of the various op-amps?

Does the DC go to 0v if you connect a woofer to each channel?

manninen · 2017-02-26 8:04 pm

drops 0,1 and 0,7

i dont have schematics yet, dont know where to measure op amps

i measured 6mV on 160.4 working rear channels

this amp idles 14w on 12volts

Perry Babin · 2017-02-26 11:17 pm

What's the PC# on the board?

manninen · 2017-02-27 5:55 am

Pc-1662-a
Such bad pictures taken too.

Perry Babin · 2017-02-27 6:12 am

I don't have that diagram. Post it here when you get it from Rockford.

The PC # may have been in the photos but I didn't have the patience/time to load all of them to try to find it.

manninen · 2017-02-27 6:17 am

Are those output transistors easy to change? theres nothing holding them? soldered to that smaller board?

Perry Babin · 2017-02-27 6:29 am

They are soldered down. Most people use a small butane torch to remove/replace the transistors. Unless you have found a shorted FET, you may not have to do anything with the MEHSA insulators.

manninen · 2017-02-27 5:25 pm

https://dl.dropboxusercontent.com/u/33080121/552/55_2.pdf

theres what i got from RF, hope it´s ok to show it here

Perry Babin · 2017-02-28 1:07 am

With the black probe on the amp's main ground terminal, what's the DC voltage on pins 4 and 8 of U101?

What's the DC voltage on pin 14 of U2?

manninen · 2017-02-28 8:23 am

that i can do, i said no sound but there try to be sound. when i turn volume up theres loud scratch.

manninen · 2018-04-04 2:45 pm

Perry Babin said:
With the black probe on the amp's main ground terminal, what's the DC voltage on pins 4 and 8 of U101?

What's the DC voltage on pin 14 of U2?

Sorry for 13months delay.

I took this to local tv/radio repair, lack of interest/no easy way out i took it back.
atleast there was no money involved to check this white elephant

U101 8 there is 13,8volts, -23,5v on PIN 4

U2 pin 14 there is 25,8 volts

Perry Babin · 2018-04-04 3:43 pm

Q9, the negative regulator, isn't working properly. Post the DC voltage on all 3 legs.Make sure that R26 and R28 are within tolerance and don't have any bad solder connections.

manninen · 2018-04-04 3:57 pm

Q9 -24.4, -26 and -24.4 from left to right.
R28 0.240kohm R26 2.4kohm

Perry Babin · 2018-04-04 4:03 pm

It appears that its defective (possibly shorted pin 1-3). This needs to be resolved. It may not solve your original problem but it is the next step.

manninen · 2018-04-04 4:11 pm

Measured much different than Q8, am i right i can compare these two?
Damn wish i had not take Q9 outta mehsa.

Well, gonna get some new lm337sp

Perry Babin · 2018-04-04 4:15 pm

I don't what you'd compare. They aren't transistors. They are complex integrated circuits and can't be easily checked with a multimeter except when they fail catastrophically. It appears that the regulator is shorted or leaking internally.

punch 55.2 dc on outputs, no sound

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