Hifonics Thor X not powering on

Dr Zeus

Member
2010-10-17 5:12 am
In trying to fix this amp, I shorted R116 and R216 to the chassis and now it wont power up. While it was shorted, the amp actually played fine but would not turn off. It got kind of hot, but not hot enough to turn on protection or pop any transistors. I see a lot of amps posted in this state with TL494CN values. I only see 12vDC at the front of the coil and 6vDC on the back. No AC at transformer coil.

TL494CN

1: 0.772
2: 5.02
3: 4.73
4: 0.215
5: 1.411
6: 3.388
7: 0
8: 12.27
9: 0
10: 0
11: 12.27
12: 12.26
13: 4.97
14: 4.96
15: 4.97
16: 11.46

Is this TL494CN working right?
 

Dr Zeus

Member
2010-10-17 5:12 am
This is unfortunately my handy work. The original R116 and R216 looked burnt so I replaced them. I did this all about a month ago; before I really started really learning how to apply myself in fixing amps. You can see I used two wire-wound 2.7 Ohm 5w resistors in place what should have been 2.7 ohm 1w resistors. Then, after soldering these in I forgot to clip the excess on the back and all 4 leads shorted to the chassis. Amazingly the amp actually played in this state for about 30 minutes until I realized it would not power off. The TL494CN is just near these resistors.

IMG_20101104_231400.jpg


Starting with the 2 large pads directly in the center of this photo; R116 and R216 leads were left uncut and shorted. The small white wire is connected to Pin7 of the TL494CN :

IMG_20101104_231420.jpg
 

Perry Babin

Member
Paid Member
2003-11-20 11:01 am
Louisiana
www.bcae1.com
Those aren't causing the problem. If the leads only shorted to the chassis, the outputs are likely the only components damaged. Have you checked the outputs again?

If the leads were long and folded back onto the board and shorted to other components, that could have caused damage to other components. Is there an 8 pin op-amp on the board near the 494?

Follow the traces from pin 16 back from the IC. It goes to the hybrid module (what's the number ON the module)?

Where does the trace go from there?
 

Dr Zeus

Member
2010-10-17 5:12 am
Just checked the outputs. Nothings shorted, and diode check seems fine on all fet and output transistors.

I dont know if the leads folded back - I cant remember exactly. When I found them that way I was able to clip them without taking the PCB off the sync so i could not tell.

Pin16 is splitting in a few different directions. First is to the resistor network (You can see that in both pictures). Second is to some glas diodes which check out fine. From the diodes the trace connects to Pin1 of the 14 pin BA10324A which is quad ground sense opAmp. On the top of the PCB is written LATCH. I think this module also does Lamps and thermal operation. Is that the hybrid module?

http://www.datasheetcatalog.org/datasheets/70/233206_DS.pdf
 

Dr Zeus

Member
2010-10-17 5:12 am
Its TLPSU-96 then. You can see it in the first 2 photos I've posted. Pin16 of the 494 is hooked into the first (Top view, left most) pin of the TLPSU.

They're not too pretty - turned a bit green but not from my doing. The amp must have been pushed really hard a long time ago. My resistor shorts did NOT cause the traces near the Fets to turn green. Continuity seems fine in all power supply areas.

I left the 494 in focus in both of these photos:
IMG_20101105_000409.jpg

IMG_20101105_000430.jpg
 

Dr Zeus

Member
2010-10-17 5:12 am
If the latch output (pin 14 on the 324) is driving pin 16, it's likely that the 324 had voltage when you read 11.46v on pin 16 of the494. Re-check your setup. If you still have 11+v on 1 and there is no voltage on pin 4, the diode may be isolating the 324 from the 494.

I cant seem to trace 324's pin 14 to the 494's pin 16, but I think I found the problem anyways.

Seems D2 is blocking 12v from hitting the 324's pin 1. I have D2 pictured a few times above, and on the left side I measure 11.8v. On the right side I measure .7v. D1 is in the same connecting trace and it is NOT blocking traffic. 12v on both sides.

Replace D2? I've got a spare 1w Zener on hand, but the package says its rated for 5v...
 

Dr Zeus

Member
2010-10-17 5:12 am
I rechecked my setup, and while the 494 has voltage readings such as the first post; the 324 reads .7v on pins 1,2,3,_,5,6,7: Here we go:

324:
1: .7
2: .7
3: .7
4: 0.000
5: .7
6: .7
7: .7
8: .043
9: .68
10: 1.9
11: 0.000
12: .68
13: 2.4
14: 2.1

I'll get a new D2 diode tomorrow and let you know. Thanks perry!
 
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Dr Zeus

Member
2010-10-17 5:12 am
Pending purchase of a diode to hopefully this this amp...

It has another problem - "When the amp was working" - the gain pot makes a lot of audible noise when touched or adjusted. Does anyone have a Generation X Camelion system-design module I can use in place of the one I have? What I have is the basic module with just gain and boost. It would be nice to have some crossover control with this amp. If you have something spare I can likely throw you a few $. Otherwise I'll have to scout around and find a replacement gain control pot.
 
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Dr Zeus

Member
2010-10-17 5:12 am
Replacing D2 didnt help at all. The old D2 measured fine on and off the pcb so I had my doubts about replacing it, but I went ahead and did so to no avail.

I dont really understand why, but the 324 is now measuring pins 2 and 4 differently:

324:
1: .7
2: 2.3
3: .7
4: .7
5: .7
6: .7
7: .7
8: .043
9: .68
10: 1.9
11: 0.000
12: .68
13: 2.4
14: 2.1
 

Dr Zeus

Member
2010-10-17 5:12 am
D2 has 12v on the cathode end and .7v on the anode.

First pic: Pin 16 from the 494 traces up to the first driver board and into a long resistor network (Screw pointing on back of PCB). It also jumps over to R8 as pictured; I removed R8 to test and then soldered it on the back of the board (easier to do that than on top of the board). R8 is fine, and feeds Q5 which feeds Q6. Both Q5 and Q6 pass DVM testing and look OK.

IMG_20101105_182942.jpg


IMG_20101105_183054.jpg
 
If pin 16 is directly connected to R8, remove R8 to see if the amp will power up.

I'd suggest clamping all transistors down before you apply power. If there's a problem that's causing it to go into protect, having everything clamped will help protect the transistors.

Does the other driver board area have a similar group of components with a resistor directly connected to pin 16?
 

Dr Zeus

Member
2010-10-17 5:12 am
I unsoldered R8. Loaded the PCB up into the sync and put on the majority of the clips. The amp still did not power up. From what I can ell everything is the same. The 324 still has 0v on pin 11. the DVM confirms that the left side of R8's connection pad is directly connected to the 494.