KLH R6200 burnt up resistor

Thread Starter

Snayke62

Joined Feb 1, 2021
49
I need help. I've read all I can find on here about this issue. I cannot find a service manual. Unit powers up for a second or so and shuts off. Only if he red led standby indicator is on. So I found a melted resistor. It seems to be in one of the transister driver circuits. I think. It's close to it anyways. So I removed it. Same situation. If I remove the two fuses for the 20v and 45v power supplies to the board. The unit will turn on and display like normal. But no sound. Anyways. I've tested transistors and every damn thing else I can find online to try. It straight up will melt a resister. Like red hot and burnt instantly. Please help.
 

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Dodgydave

Joined Jun 22, 2012
9,951
Start by giving us the make and model number of the amplifier, ..

What are the supply voltages, and what voltage is at the speaker output where the two white Resistors meet.
 
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Thread Starter

Snayke62

Joined Feb 1, 2021
49
Start by giving us the make and model number of the amplifier, ..

What are the supply voltages, and what voltage is at the speaker output where the two white Resistors meet.
It is a KLH model R6200. It is 120 VAC supply from wall to transformer. From transformer output to the main board has 6 wires that supply voltage to the PCB. 2 of them are 40.6 VAC. 2 of them are 18.5 VAC and 2 Of them are ground.
16122742445352764373369220425139.jpg
 

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Thread Starter

Snayke62

Joined Feb 1, 2021
49
I think I have some resistor at work I'll bring home. But it won't do much good to install one yet.
I'd you look at post #3 attached photo 3. That transistor on the right spears to look like it's been hot or replaced before. The solder joints on the back don't look factory either. That is the only spot other than the burnt resistors I see that look questionable. I've tried to test them in position but not sure if done it correctly. I can tell you they ohm out and diode check all the same. Far as I could tell.
 

Thread Starter

Snayke62

Joined Feb 1, 2021
49
I'd you look at post #3 attached photo 3. That transistor on the right spears to look like it's been hot or replaced before. The solder joints on the back don't look factory either. That is the only spot other than the burnt resistors I see that look questionable. I've tried to test them in position but not sure if done it correctly. I can tell you they ohm out and diode check all the same. Far as I could tell.
Sorry, I mean the one on the left. It looks worse in the photo than it is.
 

Thread Starter

Snayke62

Joined Feb 1, 2021
49
Okay. I'll take them out when I get off work. I might as well order new ones. if am going to take them out I'm going to replace them. Where is best place to get resistors and transistors?
I gotta say, I've never seen a forum be as helpful and actually have correct information and knowledge to troubleshoot some of the things I've read here that actually get fixed and a conclusion is made. I'm in the right track just from reading threads. But I wanted a guiding hand.
 

Thread Starter

Snayke62

Joined Feb 1, 2021
49
Finally got to check Q307 and Q305.
Removed both transistors....
They test OKAY ( I'm pretty confident unless I missed a check. I'll attach a photo of my work. The only thing I'm not 100% sure about.....doing a resistance test between C and the aluminum tab with the hole in it, or call it the housing if you will, is a direct short with .3 ohms. Like a good circuit would be. Normal? Nothing else has continuity to the housing like C does. Now what? My guess would be the little capacitor (c355) that is kinda melted from the resistor (r378) having a meltdown , twice. Remove and test?
 

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Thread Starter

Snayke62

Joined Feb 1, 2021
49
By the way, has anyone looked or found a schematic for this receiver? I couldn't find a damn thing hardy for anything even pertaining to model R6200. Def not a repair manual. Just wondering.
 

drc_567

Joined Dec 29, 2008
1,110
By the way, has anyone looked or found a schematic for this receiver? I couldn't find a damn thing hardy for anything even pertaining to model R6200. Def not a repair manual. Just wondering.
... looked several places, with no success. ... Assume that the circuits are proprietary, company secrets, even after many years.
... advise follow up on post #13.
 
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