Phase Linear Dual 500 Diagnosis Assistance Requested

[grapplesaw]

If you jump the collector and emitter you should get 0mv this can eliminate the bias trans one way or thevother add jumper on bad channel from pin red to brown and check. If 0 then probably transistor. If not something different is wrong. I suspect a cold solder joint

 

[grapplesaw]

Dc offset is great

 

[zeppelinofled69]

Jumping the emitter and collector on the bias transistor of the bad channel drops current to about 3mV, but not totally 0. Is that still indicative of a bad bias transistor?

 

[grapplesaw]

That Is probably the dc offset from the output pair. Yes I would change the transistors then. Do both while you are at it. Which bias transistor will you use as you need to note that the legs maybe different orientation.

 

[grapplesaw]

The same part # made by different manufacturers can have different pin outs.
Perry can tell you all about.
Here is my chart for the 2n5088 I use.

 

[zeppelinofled69]

I ordered a set of Central Semiconductor 2n3403 transistors from mouser. I will be sure to check the pin out before installing.

 

[grapplesaw]

Here is some info supplied to me on bias transistor substitutes form our member THD+N

Q118 can be replaced by a plastic T0-126 transistor such as 2SC3421. Notice that the 2SC3421 is an all plastic case transistor and you can mount the 2SC3421 directly to the heat sink with thermal grease. If you use another type of TO-126 type transistor for a bias transistor, ensure it is all plastic. If not, then you may have to use an insulator and thermal grease to ensure electrical isolation. A lot of transistors can be used for the 2N3403 bias transistor substitute. Cut the leads from the 2N3403 and solder them to the new T0-126 type transistor leads. Make sure you identify the correct pin-out of the new transistor and attach the bias wires from the 2N3403 in the correct manner. Bias will need to be readjusted when using a different type transistor. I am using 2SC3421’s now in a 700II and they work great. No issues.

 

[zeppelinofled69]

According to the datasheet, the transistors I got are TO-92HS-3 package, and have the metal clip to mount the device to the heat sink just like the original.

I assume that a lot of people sub these out for something else because of cost?... as the ones I ordered were over $5 a piece.

Any reason I should be worried about insulating this one differently that the original?

https://www.mouser.com/ProductDetail/610-2N3403

 

[grapplesaw]

All good with what you got.
I use a taser knife and split the two aluminum tabs apart down to and including the transistor base to brake the glue then punch the old one out. Put in the new one with 5 minutes epoxy. Make sure it just sticks out to ensure no contact from the leads and the tab. Ratach the leads to the new one and use the old insulators again check out the product pinout for the ones you bought

 

[grapplesaw]

I was cleaning up little projects today. One was a d-500 which caused all sorts of meter problems. I got tired of trying to fix it so I pulled the high frequency protection circuit out. It is located in the middle of the pl32 board. Today I dicided if I was to sell it had to be fully operational. Other than this problem it the rest was very good. I found there were several resistors out of spec on the power supply circuit on the board. After fixing those I repacked an rc4558 chip and upgraded a ges97 transistor with a tis97 transistor. So I checked the pinout of 97’s and found they were opposite to each other. Check those parts before you put them.

So now back together and all is good. Dc offset 4mv on left and .4 on right.
Set bias on high rail voltage to .350. .005% THD+N. Not bad for near 600 watts a channel

 

[zeppelinofled69]

That's awesome Grapplesaw.

Once the Bias is sorted, I think the last thing I need to figure out is the meters. They work and have been calibrated, but do not return to 0 without a signal. I found a snippet in the manual that states I need to check some of the diodes on the board, so I'll be pulling the front back off and testing around. I will test a bunch of the resistors as well to see if there are any out of spec. Hoping it isn't the LED driver chips, as I have not had luck finding a source for these that isn't from China.

 

[grapplesaw]

Lee and I have bought these from Germany in the past. There are sellers for this Uaa170 chip in USA Spain And other European countries on eBay. Just search UAA170

I ordered these from China
EBay # 2622162184995 for about $15 including shipping. I will test them out as needed.
They have sold several hundred of them and no neg dead back on this item.
We are using China knockoffs in the DCP 400 boards without an issue I am aware of.

 

[zeppelinofled69]

I grabbed a set of 2 from a USA seller. I'll give these a go and if it fixes the issue in one channel, I will get another set.

 

[WOPL Sniffer]

I grabbed a set of 2 from a USA seller. I'll give these a go and if it fixes the issue in one channel, I will get another set.

PM me your address, I'll send you a pair.

 

[WOPL Sniffer]

I didn't forget, just been bustin a move to get my amp completed. I'll send them tomorrow along with those outputs you wanted. No charge.... Not even for shipping

 

[WOPL Sniffer]

I used some of these but I quit repairing the series II meters since Joe's work so well.

 

[zeppelinofled69]

Well Dang, Perry, thanks a lot.

Would Joe's meter upgrades work on the 500, or is that a 400/700 thing only?

 

[WOPL Sniffer]

I don't know if you can use them or not but I'll stuff some of the .33 ohm emitter resistors in too... You can always use them to repair you blender or something.... You can never have enough parts

 

[WOPL Sniffer]

Well Dang, Perry, thanks a lot.

Would Joe's meter upgrades work on the 500, or is that a 400/700 thing only?

Glen once made a Hemi work in a moped so anything is possible.

 

[zeppelinofled69]

Glen once made a Hemi work in a moped so anything is possible.

LOL... very well.

Thanks again. Really appreciate all of the help from everyone.