KR 6170 resistor question

xpert54

Lost in Music
I recently got a Kenwood KR 6170 and found several burned resistors on the amp board. I was able to look the parts up and get them ordered.

My question is one is a .47 ohm 1 watt metal film resistor the only replacement is a .47 ohm 2 watt metal film resistor. the tech I talked to said it would work fine as long as the ohms resistance is the same.

I believe the tech but thought I'd ask the Gurus on AK to be sure as this is one project that I feel I can handle and don't want it to go up in smoke.

TIA
 
The 2 watt will be fine, but..........you NEED to find out what caused them to burn. Something was pulling to much current through them. If the cause is not found, you will end up with the same results. Or worse.........
If they are on the power amp, you have some shorted transistors. How bad are they burned? Discolored? Or blackened?
 
there was just one burned orignally and it is a 4.7 ohm carbon composition type resistor. looking at the amp and preamp board I saw where it looks like some sort of liquid was spilled on the preamp board.

At that time you could replace the 3 amp fuse and power the reciever up and it would come on for about ten seconds then blow the fuse.

I did replace the fuse one more time and it was the wrong amperage (10 amp) and that's when it burned to other two resistors. I thought I had picked up the other 3 amp fuse. A very possible costly mistake on my part.

All the resistors that burned have been pretty hot and discolored but not fried beyond telling what they are.

This reciever has been stored for the last 10 or 15 years and I got it when the owner was cleaning out his garage. He told me it was working and just quit when he went to use it later. He also has two kids that were at a young age at that time and could be how the liquid got spilled in it. That maybe what caused the original failure to occur.
 
shorted transistors will burn resistors ..so will anything shorted for that matter .. its likely very hot looking/burnt or its a power transistor with a metal case . then you wont see any burning ..
 
Thank you for all the help. I'm very much a noob at this. In reading the schematic I see there is a Round transistor called a power limiter that is before the resistor that burned up.

If I'm reading the schematic right each channel on the power board has one in each circut. Could one of these be why the resistor fried?.

I have a less than basic understanding of what I'm attempting to do but more than willing to learn.
 
Re68 4.7 ohm 1/2 watt carbon composition

Re65 .47 ohm 1 watt metal film

Re69 10 ohm 1/4 watt carbon film

Re62 33 ohm 1/4 watt insulated carbon film.

Transistor Qe 9 is on the circut that toasted the resistors and I belive is designated as a power limiter. I can see no discoloration on it and it does not look bulged nor do any of the caps on the board. Re 69 looks very discolored as if its been hot
 
Checking output transistors, part number is Hitachi 2SC1030

1. shows 1.4

2. shows 2552 and to infinity and back

3. 0 load

4. 0 load

I checked these after I pulled them from the heatsink. the two that zeroed out are next to each other as are the other two one checking out at 1.4 and the other going from infinity and back.

With what little bit I know it seems these are bad
 
OK The transistors have been pulled out of the heatsink so this is bench testing using diode mode on my DMM according to AK stickys posted by Echowars, Thanks Echowars for posting those.

The transistors are of the NPN type

1. bl to base-rl to collector=ol

2. bl to base-rl to emitter=ol

3. rl to base-bl to collector=489

4. rl to base-bl to emitter=507

the other two tests on the one transistor were ol. This is the only good one out of the 4?

All other output transistors read a .000 or a .001 and the meter kept up a constant beep while testing those
 
Yes, you have a handful of failed/damaged trannies. Replacing all four would be prudent.
 
Yep, no doubt that the outputs are bad. I have found some replacement transistors NTE280's for around $7.00 each. As soon as I can I'll be ordering those and a couple of resistors and just maybe the 6170 will live again.

thanks to those who chimed in to help me thru this. Every day is a learning experience and I learn something new everyday
 
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