Need Help! Master Buss Compressor

[Craig York]

Good day everyone. I hope you all had a great Christmas Holiday and wishing you a safe and prosperous new year.

First off, I haven't worked on anything since the days of Cell Phone Repair shops in the 90s. So I am a little rusty. I am trying to determine if I want to send this unit out for repair or if I should attempt to repair it myself. I am a serious DIY guy and hate spending money on something I could do myself. With that said, here is the problem:

The left side of my master buss compressor is significantly lower than the right and I am getting a slight hum. I am not sure where to start checking for issues. The guy I purchased this from moved to New Orleans and told me it probably needed to be re-capped and re-calibrated and recommended a shop to take it to.

I have attached some pictures of it for you to look at. What should I look for and what should I test. I still have my old Snap On volt meter I just need to know where to begin.

Thanks Fam.

 

[Bluejets]

By re-capping he would have been refering to the electrolytic capacitors.
These tend to dry internally with age and basically will no longer do the job they were intended for.
I see 18 on the top main board ( they are the ones look like cans)with another 2 underneath.(large blue casing ...main power caps)
The front panel board (from what I can see) has tantalum so no problem there.

First job would be to get replacement electrolytic caps so you will need to record the uF and voltage of each one.
Order good quality low esr caps from a reputable supplier ( not China)
Recheck the order when it arrives so you have the correct numbers etc.
Get yourself a good soldering iron, preferably one with an anti-static strap as it is unknown just what type of IC chips are on the board there and best to be on the safe side.
When you have done the above and are ready to begin I would suggest a call back here and someone will guide you through the replacement proceedure.
Happy New Year from down under (Australia)

P.S. I have no idea what a snap on voltmeter is.

 

[Craig York]

@Bluejets

Thank you so much for your reply. I truly appreciate it.

Do you recommend recapping the unit or just replacing the one(s) that are bad?

Also Snap On was a mobile tool vendor that use to come around to automotive shops and sold tools. A Voltmeter or Voltagemeter or Multimeter is what we used to to measure current. They sold a pretty decent one back then .. 25 years ago ..... seems like yesterday.

Thanks again, and happy new year to you and yours.

 

[(*steve*)]

I'd just start with the power supply caps. One looks to have a dodgy soldered joint too. Maybe just try resoldering it first.

 

[Craig York]

I'd just start with the power supply caps. One looks to have a dodgy soldered joint too. Maybe just try resoldering it first.

Are the power supply caps the larger ones? And where do you see a "dodgy soldered joint"?

 

[(*steve*)]

yes, and the only one visible. I have no idea about the other three and the photo is not good enough for me to be other than suspicious. The fact the board was not cleaned following manufacture may be the reason it looks dodgy though.

Also, when replacing caps, you want the same or higher voltage, the same our marginally higher capacitance, and one that physically fits.

 

[Craig York]

yes, and the only one visible. I have no idea about the other three and the photo is not good enough for me to be other than suspicious. The fact the board was not cleaned following manufacture may be the reason it looks dodgy though.

Also, when replacing caps, you want the same or higher voltage, the same our marginally higher capacitance, and one that physically fits.

Thank you so much. Do you recommend a dealer that sells caps? I also attached some better pictures. Do you know what those pods are?

 

[Craig York]

yes, and the only one visible. I have no idea about the other three and the photo is not good enough for me to be other than suspicious. The fact the board was not cleaned following manufacture may be the reason it looks dodgy though.

Also, when replacing caps, you want the same or higher voltage, the same our marginally higher capacitance, and one that physically fits.

Are these any good? They are the same uf and voltage.
http://www.amazon.com/Electronics-S...51618396&sr=8-1&keywords=capacitor+1000uf+63v

 

[(*steve*)]

. Do you know what those pods are?

Those are most likely the main filter caps. The solder joints look better than I thought but I think I'd resolder them anyway.

What is written on them?

 

[(*steve*)]

Are these any good? They are the same uf and voltage.

Possibly a bit on the expensive side.

Try digikey, mouser, etc.

 

[Craig York]

Those are most likely the main filter caps. The solder joints look better than I thought but I think I'd resolder them anyway.

What is written on them?

On one side it says 1000μF / 63V and on the other side it says +105 C / CE FC

 

[Craig York]

Possibly a bit on the expensive side.

Try digikey, mouser, etc.

Ok, thanks. I haven't had an opportunity to test these yet. Just found out my son took my Multimeter to school with him. So I just ordered another from Amazon. Thanks for all of your help. I truly appreciate it Steve.

 

[dorke]

Ok, thanks. I haven't had an opportunity to test these yet. Just found out my son took my Multimeter to school with him. So I just ordered another from Amazon. Thanks for all of your help. I truly appreciate it Steve.

If this is a stereo unit ,I don't think it is the PS caps.
If they were you would get the problem on both channels.

The proper instrument to test and fix this is an oscilloscope.
A "PC audio scop" could do the job as well.

There is a lot of dirt on the boards,first thing to do is clean well.
Then Inspect the soldering.

If possible mark the writings on all ICs on a photo,that could help.

 

[Craig York]

If this is a stereo unit ,I don't think it is the PS caps.
If they were you would get the problem on both channels.

The proper instrument to test and fix this is an oscilloscope.
A "PC audio scop" could do the job as well.

There is a lot of dirt om the boards,first thing to do is clean well.
Then Inspect the soldering.

If possible mark the writings on all ICs on a photo,that could help.

Thanks @dorke. I appreciate your input. I will do just that (clean the board) and check the soldering. So if I am getting a hum and one channel is lower than the other you dont believe it could be one of the "caps"?

 

[Bluejets]

No, what he said was he didn't think it would be the PS caps (PS being Power Supply...i.e. the two large caps on the back of the board.)

Reason being it appears to be a split supply which is common to both channels.

There are 18 others on the top. Could be as many as half of them that may be related to your problem though. ( some of the circuit is a duplicate of the other ...... one channel humming....one channel ok)
Get the drift..?

Thing is, one tends not to replace just 1 that you may find dodgy.

As an example found these on mouser .... http://au.mouser.com/ProductDetail/Panasonic/EEU-FC1J102/?qs=sGAEpiMZZMukHu%2bjC5l7YQ1YLJvaZJVlb2EbPdqonAY=

As a general rule, the higher the voltage, the higher the cost.
Others on the board may not be such high voltage or capacitance so much cheaper.

 

[Craig York]

No, what he said was he didn't think it would be the PS caps (PS being Power Supply...i.e. the two large caps on the back of the board.)

Reason being it appears to be a split supply which is common to both channels.

There are 18 others on the top. Could be as many as half of them that may be related to your problem though. ( some of the circuit is a duplicate of the other ...... one channel humming....one channel ok)
Get the drift..?

Thing is, one tends not to replace just 1 that you may find dodgy.

As an example found these on mouser .... http://au.mouser.com/ProductDetail/Panasonic/EEU-FC1J102/?qs=sGAEpiMZZMukHu%2bjC5l7YQ1YLJvaZJVlb2EbPdqonAY=

As a general rule, the higher the voltage, the higher the cost.
Others on the board may not be such high voltage or capacitance so much cheaper.

No, what he said was he didn't think it would be the PS caps (PS being Power Supply...i.e. the two large caps on the back of the board.)

Reason being it appears to be a split supply which is common to both channels.

There are 18 others on the top. Could be as many as half of them that may be related to your problem though. ( some of the circuit is a duplicate of the other ...... one channel humming....one channel ok)
Get the drift..?

Thing is, one tends not to replace just 1 that you may find dodgy.

As an example found these on mouser .... http://au.mouser.com/ProductDetail/Panasonic/EEU-FC1J102/?qs=sGAEpiMZZMukHu%2bjC5l7YQ1YLJvaZJVlb2EbPdqonAY=

As a general rule, the higher the voltage, the higher the cost.
Others on the board may not be such high voltage or capacitance so much cheaper.

Ok, thanks for this. I will start with replacing all the caps and take your advice and order them through mouser. This should be fun.

Can you check if the caps are good or bad while they are still connected to the board?

 

[(*steve*)]

Reason being it appears to be a split supply which is common to both channels.

I interpreted the problem to be hum on both channels and a lower output on one than the other.

I guess it's not completely clear.

The other question is "did anything happen prior to the problem starting?"

Failing caps generally go high in ESR way before they lose capacitance. In audio circuits a higher ESR (and you use an ESR meter to check them) is unlikely to cause huge problems, except in the power supply. The fact that the power supply caps are 105C rated suggest they should have a reasonably long life in a circuit like this.

A poor solder joint (or joints) on the main filter caps in the power supply could quite easily be the source of a sudden onset of hum after some sort of vibration or impact (perhaps so slight as to go otherwise unnoticed).

 

[(*steve*)]

This page may be relevant.

 

[Craig York]

I interpreted the problem to be hum on both channels and a lower output on one than the other.

I guess it's not completely clear.

The other question is "did anything happen prior to the problem starting?"

Failing caps generally go high in ESR way before they lose capacitance. In audio circuits a higher ESR (and you use an ESR meter to check them) is unlikely to cause huge problems, except in the power supply. The fact that the power supply caps are 105C rated suggest they should have a reasonably long life in a circuit like this.

A poor solder joint (or joints) on the main filter caps in the power supply could quite easily be the source of a sudden onset of hum after some sort of vibration or impact (perhaps so slight as to go otherwise unnoticed).

The hum is on both channels yet the left channel is the one that is significantly lower than the right.

I did notice this after moving from one studio to the next. The problem is that I didnt hook up the compressor until months after the move because we replaced a lot of our hardware with a lot of software plugins. And now that I think about it, I really need to hook it back up to be sure the humming was on both channels and not just one. But it was definitely after we moved. My meter should be her tomorrow so I will start trying to diagnose the problem in this order:

1. clean the board
2. check solder
3. check the caps

I will post my finds with pictures within a couple of days for more direction.

Thanks everyone for your help. You guys are great!

 

[Craig York]

This page may be relevant.

Very Relevant! Thanks for this.