My First Phase Linear Restore- New Guy to the Forum

[laatsch55]

Amen Dennis a hell of a core group already...

 

[NavLinear]

Welcome MJ - I was so engrossed in the conversation that I forgot to say hi. Glad to see you here. You are in good hands here - maybe a bit crazy at times but that is half the fun.

 

[mjstriker]

NavLinear- thanks for the welcome. I have been a bystander reading up on the threads here but it is sure fun to finally jump in and be a part of the crowd (and it sounds like my kind of crowd so far!)

Found a little free time to pull the top three rows of output transistors off the unit today. I assume they are the originals seeing as they are the PL909 but they sure were extra liberal with the heatsink goop. I also realized how loose they were after all this time so I tightened up the bottom row.

My question is are the output transistors suppose to be soldered on? They basically feel off once the screws were taken out and since they looked like originals I figured the hadn't been messed with but you never know. I bought the unit from the original owner who said nothing had been done but you never know with that sort of stuff. Anyways I thought I had read somewhere that they were soldered but I figured someone here would have the correct answer for me.

So the next step is to get the new transistors in the unit when I get a little more free time

On a side note I checked the resistance on the speaker outputs and I am registering the 5.6 ohm as expected.

 

[laatsch55]

Standard D-9's then. MJ, after 40 plus years, the TO-3 sockets are almost guaranteed to be loose. With the XPL out GENTLY squeeze the iris that bites the leads. If some were soldered in then you know they were loose. Soldering was not done at the factory. With Joe's new backplane board there are no sockets...

 

[mjstriker]

So I am getting ready to put the new outputs in. Cleaned up the back panel and remove all that sticky compound. I also pinched the pins a little to tighten up the contacts. I have some arctic 5 thermal compound left over from a redo on my computer heatsinks. My question is whether I can use that type of compound on the amp. I know there are some issues with some thermal compound that conducts electricity and would be bad for outputs on amps.

 

[frhodes]

So I am getting ready to put the new outputs in. Cleaned up the back panel and remove all that sticky compound. I also pinched the pins a little to tighten up the contacts. I have some arctic 5 thermal compound left over from a redo on my computer heatsinks. My question is whether I can use that type of compound on the amp. I know there are some issues with some thermal compound that conducts electricity and would be bad for outputs on amps.

NO NO NO

Arctic 5 contains silver. Make amp go boom.

You need white silicone thermal compound.

 

[mjstriker]

That was what I was gathering from my research into the thermal compound needed. Any ideas on some local stores I could grab this at. Have a free afternoon coming up to work on the unit. It would be a bummer if I miss it cause I have to wait for some to be shipped in. Thanks

 

[laatsch55]

Anyone that carries NTE stuff will have it, maybe the "Shack" too.

 

[NavLinear]

I just went online to see where you could get this and it Radio Shack carries a silicone based heat sink compound. Do you have any electronic stores in your area?

The basic premise behind using the thermally conductive grease is to fill air gaps that exist due to imperfections of the mating surfaces. A very thin layer on both sides of the mica is all you need.

Heat sink compound is a much better thermal conductor than air.

Aluminum and mica are a better thermal conductor than heat sink compound.

 

[mjstriker]

Made the trek to RadioShack and the had some of the heatsinks compound that is non conductive (electricity-wise) so should be set to work on the unit this afternoon after work. Gonna build a light bulb test also. Will update when I get all the outputs back in.

 

[laatsch55]

A dim bulb tester is a must. Remember, a variac will limit voltage, but not current. Joe has a different method where he inserts a 200 ohm resistor in series with the outputs, but that doesn't have the immediate visual indication like the bulb does.

 

[Michael F]

where he inserts a 200 ohm resistor in series with the outputs, but that doesn't have the immediate visual indication like the bulb does.

You mean in place of the B+/- rail fuses, yes?

 

[laatsch55]

Nope, leave the fuses in.

 

[mjstriker]

Finally had the chance to swap the outputs. Actually web pretty smoothly and wasn't too messy. I also put together the dim bulb tester in which the phase linear passed. Hooked it back up to the system with the D9's and it played great!! Let it play for a couple hours and to me it seemed like the unit didn't heat up near as much as before.

Going to enjoy it for a little while and then look into replacing the driver board.

Thanks for everyone's help and I am looking forward to some great phase linear sound

 

[mjstriker]

Ran into a hiccup today. Was playing some Christmas music inside with the amp hooked up. All of a sudden the sound became very distorted and I quickly ran to shut it off. It seems to have blown one of the line fuses so I am thinking now I blew a few transistors also. So it looks like the amp will have to make its way back the the work bench so I can try to find which transistors are good and bad.

My question is seeing as the top half of the outputs are brand new could there be another source for my my problem? I don't want to put new outputs in to find they are just going to blow again. Don't have the change yet to throw a new driver board in along with going full comp but it looks like I am heading that way. Just wanted to see if there was something I could be doing in the meantime to prevent this problem before I make the full conversion.

Thanks and Merry Christmas!!!

 

[mjstriker]

Another quick question. For the Dim Bulb test should the bulb go dim almost immediately or stay bright? I have alway been under the impression it should go dim but a few people that have been helping me with some other electronics say otherwise and now they have gotten me confused.

 

[laatsch55]

Ih the power supply caps have discharged the bulb should stay bright for a couple seconds then gradually go dim. What does your fuse look like. Just a slow burn into or did it go nuclear?? A rail fuse going in a 400 is not that rare an occurance. What are your offset and bias measurements?

 

[Northwinds]

A rail fuse going in a 400 is not that rare an occurance. What are your offset and bias measurements?

I am WELL versed with this LOL, no problems anymore after I put 8amp fastblo's in and man, a few times I expected one to go. My dbx DX5 CD player has a Dynamic Recovery circuit and the transients hit hard when the control is maxed. Meters were sitting around mid sweep steady and then next thing I knew it was in the +3 range instantly. No fuses went but I am prepared, bought a couple packages

I love this amp

 

[mjstriker]

I love this amp

Heck Ya!!!. Really have enjoyed working on the is Amp and is does kick some major butt with my D9's hooked up to it. Can't wait to go full comp with a new driver board

Anyways the fuse has a nice black ring around it but not totally black. I swapped in a brand new one. Who knows how long that fuse had been in there. I checked the offset real quick and I am sitting 22mV and 28mV, left and right respectively. Not the greatest but not too bad. Didn't have time to check the bias as I am locked into Christmas decorating duty now. I plugged it in with some test speakers and it played very well. Maybe I the fuse just decided to go.
When I get a chance I'll check the outputs.

Music just doesn't sound quite the same without the PL in the mix

 

[laatsch55]

Hookay, check the bias first chance ya get...