Phase Linear 400 Pre-Amp. Can anyone tell me if this has been under the iron?

AintBeenDead

AintBeenDead

Active Member
Phase Linear 4000 Pre-Amp. Can anyone tell me if this has been under the iron?

* 4000 I mean (wish you could edit titles)

Picked this up today. From what I've read, it's fairly prone to failure, and loose solders. It had a sticker on the back from an old audio tech shop that closed about 15 years ago. I'm just wondering initially, if it was in for service at one point, or they just sold it.

So with that, can anyone tell if it looks to be re-capped, etc. anywhere? I can't find a pic of one open, and original.
 

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I will get you pictures of the 4000 I have sitting here. It has not been re-capped. The only thing thats been done to the one here is the 4,000 solder joints on the bottom side have been re-flowed and the controls cleaned.


I've got almost no experience with these, outside of the one sitting here. The only thing that I see obviously different is you have 2 power supply caps and this has one. The one I have looks like the ones in yours. the rest of the caps look an awful lot like what I see here.
 
On the third board from the bottom of the photo, it looks like the 2 axial caps to the right of the board have been replaced. I'm guessing that the boards SHOULD be identical if it's all original. Since the other boards aren't in pairs, have no idea about the rest.
 
Thanks guys, appreciate any useful input. Just trying to gauge if it's safe enough to try and test at this point. Or if it looks like any troubled areas have been worked on possibly.
 
Drat. I'm out of AA batteries for the camera, and my phone takes horrible pictures.

You can try it, but keep the volume on the amplifier way down. The 4000 I have here made cracking noises so loud that I thought it was going blow a speaker before I re-flowed the joints. Of course, I happened to have had it plugged into the companion amp that makes 350 wpc, so you can imagine how loud that was. If you look at how its constructed, its pretty easy to understand why it would have solder problems on the main board. I might suggest pulling the bottom plate off and having a close look at the rows of pins on those connectors for cracks.
 
gadget73 said:
Drat. I'm out of AA batteries for the camera, and my phone takes horrible pictures.

You can try it, but keep the volume on the amplifier way down. The 4000 I have here made cracking noises so loud that I thought it was going blow a speaker before I re-flowed the joints. Of course, I happened to have had it plugged into the companion amp that makes 350 wpc, so you can imagine how loud that was. If you look at how its constructed, its pretty easy to understand why it would have solder problems on the main board. I might suggest pulling the bottom plate off and having a close look at the rows of pins on those connectors for cracks.
Click to expand...

Okay, I'll just do a ton of re-flows along with clean-up. Now, are we talking all those vertical sheets are likely suspect? or just where they connect to the bottom?
 
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Yikes! I see what you all mean. I've never seen more loose solders, or potentially problematic solder traces in any unit. I think I'll be setting this aside for long weekend solder sessions. Gonna take awhile to get this where I'm confident with it :)
 
You can dig up 'soldering' posts in the DIY forum.

In my opinion 'soldering' is like putting a golf ball. If you do a lot of it it's almost second nature, yet the pro's practice, you don't have to plug the iron in to tell if you're not accurate on any given day. And or if you just don't feel like it is easy enough not to bother with it. There is no substitute for being accurate just to have go back in doubt, later. Keep notes and pics are always a good reference.

And regardless.. just check to make sure higher voltage caps are not holding any charges.
 
Binkman said:
You can dig up 'soldering' posts in the DIY forum.

In my opinion 'soldering' is like putting a golf ball. If you do a lot of it it's almost second nature, yet the pro's practice, you don't have to plug the iron in to tell if you're not accurate on any given day. And or if you just don't feel like it is easy enough not to bother with it. There is no substitute for being accurate just to have go back in doubt, later. Keep notes and pics are always a good reference.

And regardless.. just check to make sure higher voltage caps are not holding any charges.
Click to expand...

Agreed, I did mean confidence in the amp in this case though :) In my two plus years of an apparently endless old audio addiction, I've definitely gotten my soldering down pretty good. Especially now that I seem to just re-flow every damn thing in sight on every unit I get. But I usually have little pockets of 20-30 minutes here and there during the week. This one will take a little more focus I think.

And thanks for the cap discharge reminder. I've always been careful, but did have a scare about a year ago with NAD power amp I was trying to fix. Thought I was safe doing what I was doing, I was wrong. Thankfully It just charred the pcb a bit, and not my heart :thmbsp:

But I think for all the people like me, who are still very wet behind the ears. A reminder from the more experienced about the dangers of caps, or working on live gear should be CONSTANTLY repeated.
 
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AintBeenDead said:
Okay, I'll just do a ton of re-flows along with clean-up. Now, are we talking all those vertical sheets are likely suspect? or just where they connect to the bottom?
Click to expand...

I think I had one cracked joint on a plug-in board. It was actually on the phono board if I'm not mistaken. All of the rest were problems on the main bottom board. And yeah, its messy inside. Working, it sounds pretty good but the physical construction, for me at least, leaves a lot to be desired.
 
If the solder joints going to the tone amp board part of it are loose, the pre can put a wall to wall 48KHZ square wave throughout the pre amp. Joe at White Oak Audio owns one and recently was in the process of troubleshooting it and this occured on his also. Be very careful testing this preamp with any amp and speakers. If you have a scope , scope the output first, 4000's in questionable shape will also exhibit massive (well for a pre) amounts of DC offset in the range of 150-250MV. That much offset at the input to an amp will create some interesting outputs to a speaker.....
 
The service bulletin section of a 4000 manual is almost as thick as the manual. There were a LOT of changes during the 4000's life and at least 6 different versions. The 2 main ones being how the motherboard was mounted to the front plate. The 4000 is not a paragon of crosstalk. IMHO, a persons time and energy cn be used to a lot better results working on something else, like a Spec 1 , or a 3300 Ser II, or the later 3600 and 3800. Now those are some very undere the radar pre-amps. All 3 afire mentioned pre's can benefit in the frequency response department by replacing a few mylar and ceramic caps with some different value polypros....
 
laatsch55 said:
If the solder joints going to the tone amp board part of it are loose, the pre can put a wall to wall 48KHZ square wave throughout the pre amp. Joe at White Oak Audio owns one and recently was in the process of troubleshooting it and this occured on his also. Be very careful testing this preamp with any amp and speakers. If you have a scope , scope the output first, 4000's in questionable shape will also exhibit massive (well for a pre) amounts of DC offset in the range of 150-250MV. That much offset at the input to an amp will create some interesting outputs to a speaker.....
Click to expand...

I wonder if thats part of why some of the things on my friend's 700-II were bad. He had it set for direct coupling. I set it for cap coupling just in case something misbehaves.
 
The direct/normal coupling switch was to limit the low frequency going into the inputs. IIRC the normal position rolled of anything below 8hz..
 
laatsch55 said:
The service bulletin section of a 4000 manual is almost as thick as the manual. There were a LOT of changes during the 4000's life and at least 6 different versions. The 2 main ones being how the motherboard was mounted to the front plate. The 4000 is not a paragon of crosstalk. IMHO, a persons time and energy cn be used to a lot better results working on something else, like a Spec 1 , or a 3300 Ser II, or the later 3600 and 3800. Now those are some very undere the radar pre-amps. All 3 afire mentioned pre's can benefit in the frequency response department by replacing a few mylar and ceramic caps with some different value polypros....
Click to expand...

Yeah, I read for about an hour straight on this unit all over the net last night. It sounds to me like this will be exactly what I'm NOT looking for in a pre-amp. I keep reading that even fully restored it tends to be rather noisy, and it would have to pre-pre'd with another phono pre for my MC cart. I think I'll save myself the pain, and pass this one on to someone else. They definitely seem to have value for a lot of people, but I'm very confident this isn't the unit for me :(

Sure looks cool though ;)
 
laatsch55 said:
The direct/normal coupling switch was to limit the low frequency going into the inputs. IIRC the normal position rolled of anything below 8hz..
Click to expand...

I'm just thinking DC offset + direct coupling probably doesn't do good things. Remember, tube guy here, so I'm used to considering the possible hazards of DC voltage on the grid of the tube. I don't know if it would do bad things to the op amp or what. Even if not, my friend does not need to attempt to reproduce below 8 hz anyway.
 
laatsch55 said:
The service bulletin section of a 4000 manual is almost as thick as the manual. There were a LOT of changes during the 4000's life and at least 6 different versions. The 2 main ones being how the motherboard was mounted to the front plate. The 4000 is not a paragon of crosstalk. IMHO, a persons time and energy cn be used to a lot better results working on something else, like a Spec 1 , or a 3300 Ser II, or the later 3600 and 3800. Now those are some very undere the radar pre-amps. All 3 afire mentioned pre's can benefit in the frequency response department by replacing a few mylar and ceramic caps with some different value polypros....
Click to expand...

I can agree with lee. He restored a 3600 for me and it teamed up with the white oak upgraded 700b is amazing sounding with a great mm and mc phono section. I just got a 3800 now . Waiting on it to arrive. But the 3800 is supposed to have even a better phono section. So when that arrives lee will restore it for me and see what better spec's it can get...
 
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