The Fleatique Phase Linear 700 B

[BMWR75]

OK -- I pulled both of the new Q4s I had installed backwards and tested them. The one on the left side of the board was fine, the one on the right is shorted.

Did me installing the Q4s backwards cause R16 connected to the emitter of Q5 to smoke itself?

So, I installed a new MPSA92 in the right side Q4 position and put the left side MPSA92 back in too (both oriented correctly this time).

After doing that, redid the in circuit test results for Q5 on both sides of the board.

Right side of the board when looking at the component side (I am assuming this is the right channel)

Q5 base to emitter = 0.55 V forward bias and 0.83 reverse bias (this is the side connected to the smoked R16)
Q5 base to collector = 0.54 V forward bias and 0L reverse bias

Left side of board

Q5 base to emitter = 0.54 V forward bias and 0.82 reverse bias
Q5 base to collector = 0.53 V forward bias and 0L reverse bias

 

[Gepetto]

OK -- I pulled both of the new Q4s I had installed backwards and tested them. The one on the left side of the board was fine, the one on the right is shorted.

Did me installing the Q4s backwards cause R16 connected to the emitter of Q5 to smoke itself?

So, I installed a new MPSA92 in the right side Q4 position and put the left side MPSA92 back in too (both oriented correctly this time).

After doing that, redid the in circuit test results for Q5 on both sides of the board.

Right side of the board when looking at the component side (I am assuming this is the right channel)

Q5 base to emitter = 0.55 V forward bias and 0.83 reverse bias (this is the side connected to the smoked R16)
Q5 base to collector = 0.54 V forward bias and 0L reverse bias

Left side of board

Q5 base to emitter = 0.54 V forward bias and 0.82 reverse bias
Q5 base to collector = 0.53 V forward bias and 0L reverse bias

Yes having a shorted Q4 will cause R16 to smoke if at the same time D4 or D5 was open, which it was in your case.

 

[BMWR75]

Actually NTE sells a better one NTE part number-NTE401.

The best price I found so far on these NTEs is ~$12.00 each.

http://www.mcmelectronics.com/product/NTE-ELECTRONICS-NTE401-/NTE401

Ever tried these, they run $3.23 each?

http://www.mouser.com/ProductDetail...GAEpiMZZMttgyDkZ5Wiup89a9Og%2b4dEXyMv2WNTRJs=

 

[Gepetto]

The best price I found so far on these NTEs is ~$12.00 each.

http://www.mcmelectronics.com/product/NTE-ELECTRONICS-NTE401-/NTE401

Ever tried these, they run $3.23 each?

http://www.mouser.com/ProductDetail...GAEpiMZZMttgyDkZ5Wiup89a9Og%2b4dEXyMv2WNTRJs=

Same deal just less expensive because of no NTE resale markup.

 

[laatsch55]

So Avid makes the 3 finners now??? I get the NTE's local for 5.00 each. They almost had to send the very first ordedr of them back though. I wasn't paying 10.00 each. I had ordered 20.

 

[laatsch55]

Just got a woody looking over Avid's cold plate options..

 

[Gepetto]

So Avid makes the 3 finners now??? I get the NTE's local for 5.00 each. They almost had to send the very first ordedr of them back though. I wasn't paying 10.00 each. I had ordered 20.

They always did Lee. NTE just packages up other mfrs products and markets them to the repair guys in onesy-twosys.

 

[BMWR75]

Am trying to get a Mouser parts order together today so it will hopefully be delivered by next weekend.

Retested all the small diodes on the PCB PL20. On the left side of the board, D1 D2 and D18 failed the reverse bias test (e.g., I got a voltage reading instead of 0L). On the right side, D1 and D2 failed the reverse bias test.

D5 on the right side is open per previous test results.

D13 gives funny looking results on both forward and reverse bias tests (IIRC low voltage both ways), but I think @laatsch55 says this diode has to have one end lifted to test correctly. Didn't do that.

Question: are all these failed small diodes the same part number? Need some help with what to order to replace the bad diodes.

Question: the 1N4004s I installed on the rear board are 400 volt 1 amp versions. Is that OK?

Question: 33 ohm R16 needs to be replaced. Is a 2 watt 500 V metal film like this one what I should use? http://www.mouser.com/ProductDetail...=sGAEpiMZZMu61qfTUdNhG/4r7Iw6CIkydikjkbdzDms=

Question: I don't have many metal film resistors on hand. Are there some others I should order that are commonly used and commonly fail on this PCB?

Question: in Post 15 this was said, "Joe---and that still didn't stop the occasional "Laatsch-up". BUT-your use of the back-to-back 1N4148's on C6 DID." Please explain this for a newbie. Are two 1N4148s wired positive to negative and installed in parallel with C6?

Parts to order:

Q5 - 2N3439 diode - Mouser P/N 511-2N3439 - http://www.mouser.com/Search/ProductDetail.aspx?R=2N3439virtualkey51120000virtualkey511-2N3439

T05 heat sinks - Mouser P/N 532-322805B00 - http://www.mouser.com/Search/Produc...000Gvirtualkey53210000virtualkey532-322805B00

33 ohm resistor - Mouser P/N - ??????

small diodes????

1N4148 diode - Mouser P/N 512-1N4148 - http://www.mouser.com/Search/ProductDetail.aspx?R=1N4148virtualkey51210000virtualkey512-1N4148

 

[laatsch55]

Yes Scott all small diodes are 1N4148's. Get some extra so you can put some accross the C6 leads to make it latch-up proof. Lay the 1N4148's parallel with each other with the polarity reversed and the ends twisted tightly together and then solder those ends to the leads of C6.

D13 will test low both directions. There are also some others that require their end lifted because they are paralled to each other like D1,D2. Chec to see if the closely (by position) paired have a common point.

The 1N4004's are fine.


The 33 ohm should be 1/2 watt 1% xicon metal film.

Resistor failures are rare but not unheard of.

Q5 is the correct part number.

The TO-5 heatsink is correct.

Diode number is correct.

And this for the 33ohm http://www.mouser.com/ProductDetail/Xicon/273-33-RC/?qs=5pA9MUbQkUminX3nOk3Ybg==

 

[BMWR75]

Thanks laatsch55.

I've done no testing of the rectifier bridge and don't have a spare on hand. Although, my guess is the 87 V DC I had on the speaker outputs means the rectifier bridge is working fine.

Should I order one just for insurance? If yes, Mouser part #?

 

[laatsch55]

Any 35 amp BR bridge is fine. Quite a few listed.

 

[BMWR75]

Mouser parts shipment arrived.

I replaced the smoked R16 on the right side of the board. Also replaced Q5 on the same side.

Passed the dim bulb test. Reminder - I have all the output transistors removed from both channels.

DC offset now measures -1.8 mV on the left channel and -91.8 V on the right channel. Something is still wrong with the right channel.

Just a reminder -- the left channel was the one with all the blown outputs.

EDIT1 - OOPS!! forgot I need to replace D5 on the right side (had to read back through all the posts). Will do that now.

I've not installed the diode pairs on C6 yet, don't want to muddy the waters.

EDIT2 - replaced D5 and still have -92 V DC offset on the right channel speaker outs

What is the next troubleshooting step?

EDIT3 - Went ahead and tested Q7 and Q10 in circuit. Have not taken the time to figure out which is the emitter and collector on these transistors, so don't specify which is which on the test results below.

left channel Q7 forward bias tested 0.58 V and 0.52 V, reverse bias tested 0L and 0L
right channel Q7 forward bias tested 0.76 V and 0.71 V, reverse bias tested 0L and 0L Does this mean the right channel Q7 is suspect since it tests higher on the forward bias?

left channel Q10 forward bias tested 0.55 V and 0.58 V, reverse bias tested 0L and 0L.
right channel Q10 forward biased tested 0.54 V and 0.58 V, reverse biased tested 0L and 0L

 

[Gepetto]

Mouser parts shipment arrived.

I replaced the smoked R16 on the right side of the board. Also replaced the bad Q5 on the same side.

Passed the dim bulb test. Reminder - I have all the output transistors removed from both channels.

DC offset now measures -1.8 mV on the left channel and -91.8 V on the right channel. Something is still wrong with the right channel.

Just a reminder -- the left channel was the one with all the blown outputs.

EDIT1 - OOPS!! forgot I need to replace D5 on the right side (had to read back through all the posts). Will do that now.

I've not installed the diode pairs on C6 yet, don't want to muddy the waters.

EDIT2 - replaced D5 and still have -92 V DC offset on the right channel speaker outs

What is the next troubleshooting step?

EDIT3 - Went ahead and tested Q7 and Q10 in circuit. Have not taken the time to figure out which is the emitter and collector on these transistors, so don't specify which is which on the test results below.

left channel Q7 forward bias tested 0.58 V and 0.52 V, reverse bias tested 0L and 0L
right channel Q7 forward bias tested 0.76 V and 0.71 V, reverse bias tested 0L and 0L Does this mean the right channel Q7 is suspect since it tests higher on the forward bias?

left channel Q10 forward bias tested 0.55 V and 0.58 V, reverse bias tested 0L and 0L.
right channel Q10 forward biased tested 0.54 V and 0.58 V, reverse biased tested 0L and 0L

It seems you are only testing B-E and B-C (and E-B and C-B) with your readings. It is important to also check the C-E and E-C readings. You can have a leaky device and it still look somewhat normal from your prior tests.

 

[BMWR75]

You are correct. Can the C-E and E-C be checked with the transistors still installed in circuit?

I ask because I did this C-E and E-C test on a new Q5 (out of circuit) and got 0L (overrange) in both directions. Am assuming this means no leakage. But, did a quick check in the new Q5 just installed on the PCB and got 0L in one direction and 0.74 mV in the other.

 

[Gepetto]

You are correct. Can the C-E and E-C be checked with the transistors still installed in circuit?

I ask because I did this C-E and E-C test on a new Q5 (out of circuit) and got 0L (overrange) in both directions. Am assuming this means no leakage. But, did a quick check in the new Q5 just installed on the PCB and got 0L in one direction and 0.74 mV in the other.

That is quite normal because you have the forward biased C-B junction of Q7 in one direction that you are measuring ...

 

[laatsch55]

there will be an E-C,C-E reading in circuit based on polarity, normal stuff. If you have that much DC on the rails it is usually on the board as that much off the board pops fuses. Not that much more to check. D9,D10 OK" Q3,Q4OK?

 

[BMWR75]

Q1 and Q2 on the right side are giving low voltage readings from E-C and C-E (this isn't happening on the left side). They are both new, but may have gotten damaged when I had Q4 installed backwards. Am going to replace them both with new MPSA18s.

If that doesn't get the high voltage of the right channel speaker outs, I'll look closer at Q3 and Q4 on the right side.

Stay tuned.......

EDIT - Q1 and Q2 were both bad. Installed new MPSA18s in the Q1 and Q2 positions. Now have -9.7 mV DC offset on the right channel.

Is it time to install the diode pairs across C6 on each channel to prevent latch up?

Also, the old Q5 I pulled from the right channel ended up being good, but I went ahead and installed a now Q5 and 3-ring heat sink. Should I do the same for the left channel just for good measure?

I await the sage guidance that is forthcoming.

 

[BMWR75]

Hey Guys,

I now have a good dim bulb and <10 mV DC offset at the speaker outputs.

Is it time to reinstall the output transistors and test the DC offset again?

Thanks,
Scott

 

[Gepetto]

One row at a time starting at the bottom and advancing to the top. Stop and recheck after each row.

 

[BMWR75]

One row at a time starting at the bottom and advancing to the top. Stop and recheck after each row.

Will do. That will be tomorrow morning's project. Thanks much!!