Kenwood Kac-8104D Problem

[bigpun4fubu]

explain leakage like the resistance climbing or dropping?? should it check like an open circuit?

 

[Perry Babin]

If there is leakage, the meter's display will change when you touch the probes to the transistor's leads. If there is no leakage, there may be a blip on the display but it will go quickly back to whatever the meter reads when the probes are in contact with nothing but air.

 

[bigpun4fubu]

gotcha ill do that tomorrow afteroon when i get off work ill post my results , hopefully in a week or so ill have an oscilloscope (fingers crossed ) and thank you for your help so far

 

[bigpun4fubu]

output Q410 legs 1-2 reads open 2-3 reads 1.7 mohm but now 300k leaking i assume legs 1-3 read open
Q 412 read open or infinite across all paths
Q411 reads same as Q412
Q413 reads same as 411 and 412
is is safe to assume Q410 is bad???

 

[Perry Babin]

Read the following page and test as shown in the FET section of the page.
Basic Amplifier Repair - Transistor Test Applet Link

 

[bigpun4fubu]

first checked same as before , reading 11.16 megaohms on 2-3 on Q412 slowly climbing in value other check same as previous

 

[Perry Babin]

Did you short pins 1 and 3?

Did you get OL with one probe orientation and a different reading with the probes reversed (2-3)?

Did you check it on diode check?

Were you touching any part of the transistor or the probes?

 

[bigpun4fubu]

Q410 reading 9 mohms acr0ss pins 1-2 10 mohms across 2-3 1-3 are shorted now

 

[bigpun4fubu]

Q 412 reads OL over all paths Q411 reads OL also Q413 reads 1.805 Mohms across 1-2 pins 2-3 10.5 mohms

 

[Perry Babin]

Were you touching any part of the transistor or the probes?

It's going to be much more efficient if you answer all of the questions.

 

[bigpun4fubu]

no sir i had small alligator clips and those tiny clip leads on my meter

 

[bigpun4fubu]

pins were shorted with alligator test leads and i had the little tiny test clips on my probes to hold the transistors

 

[bigpun4fubu]

i also did the diode check got .474 one way and 0.000 the other on Q410 the others tested .474 and OL

 

[bigpun4fubu]

Q410 should be defective according to these tests the others not sure if .474 etc is an acceptable range since its below .5

 

[Perry Babin]

0.4... is OK if the reverse is OL.

It's not possible to get 0.000 and 0.474 on a transistor between legs 2 and 3 with 1 and 3 shorted. Re-check Q410.

All should read OL on ohms and diode check between leg 1 and the other legs of any individual transistor (no jumper connected).

 

[bigpun4fubu]

.451 and OL on reverse on Q410

 

[bigpun4fubu]

i now get 10.7 mohms across pins 2-3 on Q 410

 

[bigpun4fubu]

all others read as posted before and OL on ohms reading

 

[Perry Babin]

Although you should have infinite resistance there and this transistor may be defective, technically, I don't think that this would cause the problems you were having.

clip leads onto pins 1 and 2 and move the clips gently side to side. Do this without touching any metal on the leads/clips or on the transistor. Does the resistance ever change from OL?

Do this for all 4 FETs.

 

[bigpun4fubu]

no sir all OL all the time