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Phase Linear and AudioSource...Score?

gonzothegreat said:
Virtual troubleshooting time! Step right up!

Service manual @ HifiEngine (not the later model but hopefully close aside from the meters)
http://www.hifiengine.com/manuals/phase-linear/pl-400.shtml

You mentioned scratchy pots on the preamp so the power amp controls will need some deoxit as well. If the LEDs aren't dancing when you adjust the input level controls, then you probably won't hear anything out of the amp if you hooked up speakers to that channel. You wouldn't want to do that until you do the next step.

First, measure DC voltage on the speaker outputs on both channels (from red to black, right channel then left). The voltage should be under 50mv but could be close to 100v if something is hosed.

Do the LEDs flicker when the unit is turned on? Are there any burnt components hiding on the circuit board? If not, this may be something simple. Big amps often fail with smoke and flames. Do the heatsinks get warm? Are all the fuses OK?

Lots of easy things to check but lets get these out of the way.
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Gonzo,

Thanks so much for the reply.

Here is what I have done so far:

-Cleaned both input pots with deoxit, followed by faderlube. Alot of oxidation came out.
-Cleaned both input jacks in the rear with deoxit.
-Checked all fuses...Good.

I just hooked it up to my CDP.
When initially powered up, both meters are lit up in the far left corner of each with one led lit.
Equal output from both channels.
Right meter dances with input, left meter stays lit with only one led in the far left.

Nothing seems obviously burnt on the left meter board.
 
Checked the offset:

Left channel: -0.02
Right channel: 2.8

I assume the low left channel reading may be the cause for the non-dancing left channel LED's?
 
Your left channel DC offset reading looks great. The right channel is high, 2.8V would send an amp with a protect circuit into protection. That's the problem with these Phase Linears. No protect circuit, so they just dump the DC right into your speakers. In the case of an output transistor failure, your speakers get rail voltage dumped into them. Probably around 80VDC with this amp. I'm not sure if the 400 has DC offset adjust.
 
FYI HifiEngine gives you the choice of either the early or later (LED meter) model.

No offset adjustment - just bias.

Order replacement electrolytics from Digikey if you don't have fresh ones handy.

Look for marginal solder joints around large resistors & semis. Check all the semis & resistors with a DMM and compare them with the good channel. Move on to comparative voltage measurements if needed.

Any signs of previous repairs? How does the heatsink grease look? I'm going to guess dry-as-month-old-roadkill. Replace the grease & mica if needed.
 
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Jailtime said:
Your left channel DC offset reading looks great. The right channel is high, 2.8V would send an amp with a protect circuit into protection. That's the problem with these Phase Linears. No protect circuit, so they just dump the DC right into your speakers. In the case of an output transistor failure, your speakers get rail voltage dumped into them. Probably around 80VDC with this amp. I'm not sure if the 400 has DC offset adjust.
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Hey Kyle,

Thanks for the info...:thmbsp: I will try to work on it some more this weekend and report back what I dig up.
 
gonzothegreat said:
FYI HifiEngine gives you the choice of either the early or later (LED meter) model.

No offset adjustment - just bias.

Order replacement electrolytics from Digikey if you don't have fresh ones handy.

Look for marginal solder joints around large resistors & semis. Check all the semis & resistors with a DMM and compare them with the good channel. More on to comparative voltage measurements if needed.

Any signs of previous repairs? How does the heatsink grease look? I'm going to guess dry-as-month-old-roadkill. Replace the grease & mica if needed.
Click to expand...

With the rep these amps have, should I just order a recap and semi kits that I have seen on that auction site or just try to chase and repair what is causing the problem that I am having now...:scratch2:

Looks as if it came from the factory inside, no sign of any other hands inside near as I can tell.

I have not checked the heatsink grease yet...I will this weekend :thmbsp:
 
Steelman said:
With the rep these amps have, should I just order a recap and semi kits that I have seen on that auction site or just try to chase and repair what is causing the problem that I am having now...:scratch2
Click to expand...

You want to find exactly what is causing your problems first. Fix those issues, you don't want to shotgun all the caps and semiconductors in the amp and hope that your problem gets fixed. You can cause more issues that way. Take 'er slow, and ask questions if you don't know exactly what to do.
 
The Series II amps have a number of factory updates and I've developed a few over the years. I also have an output relay that senses DC. It's designed specifically for the 400 and mounts on top of the binding posts which eliminates any drilling. I tested it repeatedly by shorting the output transistors with a knife switch and the speaker was never hurt.

I don't think I've seen an amp with 2 VDC on the output. It's an easy fix and will take care of itself when the updates are done. All that's needed is a soldering iron and some solder wick.

I've got the service manual on pdf. You can get pics of the relay at my web site. It's long past due for update but it's functional. Send me a PM with a good email for a 5m file and I'll send the manual.

Phase Linear site
 
Just found a upgrade and repair transistor kit from LDX Technologies on the auction site for $150.00...is this reasonable or out of the question?
 
d3imlay said:
The Series II amps have a number of factory updates and I've developed a few over the years. I also have an output relay that senses DC. It's designed specifically for the 400 and mounts on top of the binding posts which eliminates any drilling. I tested it repeatedly by shorting the output transistors with a knife switch and the speaker was never hurt.

I don't think I've seen an amp with 2 VDC on the output. It's an easy fix and will take care of itself when the updates are done. All that's needed is a soldering iron and some solder wick.

I've got the service manual on pdf. You can get pics of the relay at my web site. It's long past due for update but it's functional. Send me a PM with a good email for a 5m file and I'll send the manual.

Phase Linear site
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Thanks very much...PM inbound.
 
Steelman said:
Just found a upgrade and repair transistor kit from LDX Technologies on the auction site for $150.00...is this reasonable or out of the question?
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That looks like a pretty serious upgrade kit! If you know for sure that you have bad outputs then this would be a good solution.

IMHO since you have one good channel and no visible damage, I'd strongly suggest trying to fix it yourself unless you have $150 burning a hole in your pocket.
 
gonzothegreat said:
That looks like a pretty serious upgrade kit! If you know for sure that you have bad outputs then this would be a good solution.

IMHO since you have one good channel and no visible damage, I'd strongly suggest trying to fix it yourself unless you have $150 burning a hole in your pocket.
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Burning a hole in my pocket...I wish! :D

I read the service manual and due to my lack of knowledge and equipment, I am embarrassed to say...all I was able preform was the most basic of tests...offset check at the speaker outputs. I set my Fluke 77 Series II to the 300mV test setting and recorded the following:

Left Channel: -00.7
Right Channel: 0.27

I was unable to locate R127 to check for excess bias. I did locate R127 on the interconnect schematic (diagram 2-7) but sadly, not in the amp itself.
 
Steelman said:
I set my Fluke 77 Series II to the 300mV test setting and recorded the following:

Left Channel: -00.7
Right Channel: 0.27

I was unable to locate R127 to check for excess bias. I did locate R127 on the interconnect schematic (diagram 2-7) but sadly, not in the amp itself.
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Just to be clear, its the left channel that is not putting out any sound and your measurements are

Left: 00.7 millivolts
Right: .27 millivolts

or did you mean

Left: 00.7 volts (ie 700 millivolts)
Right: .27 volts (ie 270 millivolts)

iirc your Fluke meter will autorange on voltage unless you have it set to the 300mv range.

The bias pots are the blue and brown devices next to the large square heatsinks with the circular metal transistors. I wouldn't mess with them except to clean or replace.

phaselinear400bias.jpg


I'd check for bad solder joints around the aforementioned transistors, by the large rectangular white resistors on the left of the board and the 2 large brown resistors on the circuit board. The transistor sockets on the right should be checked as should their associated resistors. Large carbon comp resistors often go off-tolerance or physically crack.
 
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Gonzo,

Thanks again for your help.

I had my Fluke set to the 300mv range when I recorded the readings.

Thanks again for the direction. I have my kids today and I will not be able to check for those bad solder joints until tomorrow or Tuesday. I will post back as soon as I do.

Again, thanks very much. Help like this with pictures is a invaluable it me.
 
Looking at the picture Gonzo... sent, the resistor to measure the bias is just to the right of the driver board and has color bands brown-black-silver. Your amp may be slightly different as there are a couple variations depending on the age of the amp.

I'd hold off on the parts kit for the time being.
 
d3imlay said:
Looking at the picture Gonzo... sent, the resistor to measure the bias is just to the right of the driver board and has color bands brown-black-silver. Your amp may be slightly different as there are a couple variations depending on the age of the amp.

I'd hold off on the parts kit for the time being.
Click to expand...

Will do...:thmbsp: I will post back as soon as I can check the above mentioned...
 
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