Sherwood RV-5030R VAPORIZING mains fuse

[petehall347]

C1027 or A1032 are main channel drivers
hang on ..no they arent ..hold on ..
i cant find them anywhere now...
can you take a pic or point them out on schem ?

 

[Bassblaster]

C1027 or A1032 are main channel drivers
hang on ..no they arent ..hold on ..
i cant find them anywhere now...
can you take a pic or point them out on schem ?

Standby, im going to compare schem to the actual unit. try to figure out WHAT is going on here

 

[Bassblaster]

so to make sure this is the center channel i stuck my meters probe into the center speakers output plug on the back and touched the pads and this IS the center channel.
so what i found is the A1023 and C1027 dont look like the drivers... im not sure what they are but it LOOKS like the KTA's collector hooks to the emitter on the B688 and the KTC's collector hooks to the emitter on the D718.

Q113
Q114
are the drivers

Nope. because those are the KT's that tap onto the outputs collectors. so the schem is WRONG

So WHAT is going on here? and what could have cause these KT's to turn into a blob. tested them on diode test with me meter and im getting a 4mV drop across all leads any way around.

The C2235 and A965 i am not finding around the outputs.

 

[petehall347]

follow back from outputs bases to find drivers emitters

 

[Bassblaster]

follow back from outputs bases to find drivers emitters

D718's base connects the KTC's emitter AND KTA's emitter after going through a 220 Ohm resistor and a film cap in parallel with the resistor. if i touch the base pads of both outputs i get 220ish ohms between them.

 

[petehall347]

says 220 ohms on schem plot thickens ..
maybe c155 went bad ..
r163 is all you should see if outputs and drivers removed .. r163 220 ohms

 

[Bassblaster]

says 220 ohms on schem plot thickens ..
maybe c155 went bad ..
r163 is all you should see if outputs and drivers removed .. r163 220 ohms

they are 220. that was a typo. let me correct that before we get anymore confused.

 

[petehall347]

so all in all in all it needs new drivers .. more confusion i nearly said bd139 bd140 but i dont like voltage specs although they will likely survive .. maybe look at some mje next .. or tip something .

 

[Bassblaster]

but what are the KTC's and KTA's? still no luck on the drivers. just some TO-92's around but they are all C3200 and C3196 or 8. cant tell text is too small.

i guess now ill look for a tranny with a 220pF cap attached to it

 

[Bassblaster]

Well, there ARE 220pF caps attached to some transistors...they are the KTA and KTC. so they ARE the drivers?!???
EDIT: holy shit that 220 Ohm resistor and film cap is in the correct spot on the schem. WELL OK THEN. soooo schem is correct BUT just had the wrong name.. now the search for replacements for the KTA1023 and KTC1027 begin! anything else i should pull and test first?

 

[petehall347]

test the one in the middle to the left with dotted circle around it

 

[Bassblaster]

test the one in the middle to the left with dotted circle around it

Q112 C4137 is also blown. and yes its actually is the C4137 on the real unit.
Looks like the ENTIRE center channel is shot.

 

[petehall347]

yes it appears that way ..best renew all transistors in that channel and check resistors .

 

[ggregg]

I'm impressed BB. Carry on.

 

[Bassblaster]

Unless more is fried farther back in the circuit all we gotta do now is find replacements for the KTA1023, KTC1027 and C4137. for the drivers i dont see why the BD139 and 140 wouldn't work, thing is i dont know the supply voltage of this unit. the 63V filter caps would suggest 50V at least. Roughly how much voltage is needed for around 80W into 8 Ohms?
but i like how those BD's are TO-126 yet mouser and datesheet say SOT-23. im not entirely sure thats correct lol

 

[petehall347]

SOT-23 saves space

 

[Bassblaster]

cant say ive made much progress. this is as far as ive gotten.
EDIT: Testing the working C4137's on the unit they have an HFE of around 1.2K. the mouser search i did didn't do any good, i don't think an HFE of 7 is going to cut it...

 

[Bassblaster]

More progress. now with the center channel removed, i can now have both the power connectors in and it will power on without the DBT turning into a strobe light. but it still shuts off after 4 seconds. i can hear the relay disengage.

With the drivers, i might just use the BD139 and 140. i doubt the center channel is ever going to be used again anyway but...at least it should work.

 

[petehall347]

is it speaker or power relay clicking ?

 

[Bassblaster]

is it speaker or power relay clicking ?

in 74% sure its the power relay. when i turn it on i never get a 2nd click