TOA BG-130 Amplifier power supply fuse blown

[Andrew F. Ali]

Re: TOA BG-130 Amplifier power supply fuse blown

Good job!!!

[madan1]

Re: TOA BG-130 Amplifier power supply fuse blown

did you check the emitter resistors? usually they fail with the transistors.

[fuxxy]

Re: TOA BG-130 Amplifier power supply fuse blown

FIXED!
Thanks guys!

Since I was fixing this for free, I just wanted to get it over with.
I purchased a single complimentary pair of transistors from Fry's (NTE54 & NTE55), and installed them, replacing both in the pair of the side that went bad.

Reinstalled the zeners, and the resistor, and it powers on and works now!

[petehall347]

Re: TOA BG-130 Amplifier power supply fuse blown

mje are a good replacement .. bd for drivers . eg bd139 140 ..mje15003 15004 ... top of my head thinking there so check the specs before proceeding .... these should be in stock from reputable dealers ... sack nte ..

[R_J]

Re: TOA BG-130 Amplifier power supply fuse blown

I'm sure you can run it without the one set of transistors, would be the 15 watt version. The problem with the nte is you need mounting hardware to insulate the tab (collector) I would find an alternative that had the isolated case
UTsource has the ktb1367-y for $1.51 each, and ktd2059 for $1.67
there are eb sellers that have them also, one even has 2 of each for $16.95

[fuxxy]

Re: TOA BG-130 Amplifier power supply fuse blown

All those components were tested out of circuit.

Output of the primary transformer is right at 40v

Would I be able to run this amp with one complementary pair of transistors, and the other set removed?

If I can't find a source for the KEC B1367, can I replace it individually with the NTE equivalent - or would I need to replace both in the pair?

EDIT:
I'm showing the NTE replacement for the D2059 is NTE54, and the B1367 is NTE55 - Do you guys agree?

[R_J]

Re: TOA BG-130 Amplifier power supply fuse blown

the diodes would be 15 volt zeners, they seem to be in series, so thats around 30 volts, Not sure what the voltage is on the main filter but i would guess aroud 40-50 volts, I suspect the resistor is ok, it is discolored but my guess is 680 ohm
I would remove that #2 2sb1367 and check it out of circuit, I suspect its bad,
It looks like the 2 npn outputs are driven by one driver, through its own base resistor and the 2 pnp's are driven a similar way
I bet the BG-115 only has on each npn & pnp and this being the 30 watt version uses 2 transistors in parallel, I know what I would do to check the amp
I suspect you found the problem, those readings are enough to cause the amp to draw too much current but not being a dead short did not blow the 3 amp dc fuse, thats my guess,

[Andrew F. Ali]

Re: TOA BG-130 Amplifier power supply fuse blown

Looking like a 1K resistor and something is wrong with that 2nd 2SB 1367 PNP Transistor. These reading were taken in or out of circuit??

[fuxxy]

Re: TOA BG-130 Amplifier power supply fuse blown

So I checked the main power transistors (attached to the heatsink) using the "Diode" function on my DMM.
The results are a little confusing.

The first two D2059 transistors have similar results.

Pins 1 & 2 = .538
Pins 1 & 3 = .541

Pins 1 & 2 = .540
Pins 1 & 3 = .542

I get no other readings ("OL") using any other polarity or pins

The second two B1367 transistors are wildly different from each other

B1367 #1
Pins 1 & 2 = .523
Pins 1 & 3 = .525
No other readings using opposite polarity, like the D2059's.

B1367 #2
Pins 1 & 2 = .027 (Both polarities - odd!)
Pins 1 & 3 = .463
Pins 2 & 3 = .459 (Didnt get this read on the other B1367!)

-------------------------

D110 is a "15b2" silkscreened label
Reads "OL" one polarity, 0.650v the other way

D109 is a "15b2" silkscreened label
Reads "OL" one polarity, 0.642v the other way

-------------------------

R179 i can't identify. I've included a pic so you guys maybe can read what exact colors those might be
It reads 0.664 kOhm with my multimeter.

[R_J]

Re: TOA BG-130 Amplifier power supply fuse blown

That second output transformer is for driving multiple speakers that are a long way from the amp, like in a large store 25 volt or 75 volt line. the speakers would also have a small transformer on them with multiple taps.
or if you want to connect just a speaker direct you would use the com and 4ohm
I would think the outputs are fine.
I wonder if d109 & d110 are maybe zeners and are bad, It looks like the voltage from the main cap. goes through r179 and is droped by the 2 diodes which seem to be connected in series.

[fuxxy]

Re: TOA BG-130 Amplifier power supply fuse blown

Looking at the board layout, it appears that all 4 output wires on the second transformer connect directly to the speaker output terminals of the amp, but at varying voltages.

[fuxxy]

Re: TOA BG-130 Amplifier power supply fuse blown

I'll have to repeat the test. I know I tested in "beep" mode, and then again in "pure ohm" mode.

There is two transformers, but the secondary transformer has multiple secondary windings and I'm honestly out of my element as to it's purpose.

[Andrew F. Ali]

Re: TOA BG-130 Amplifier power supply fuse blown

If your multimeter is DMM then use the Diode scale to check the transistors. If you have analogue multimeter ( the one with the needle pointer) use the Rx1k scale. You would have to remove them from the circuit for testing, but you said you are not getting any shorts on the pins, so I'll say that is not the cause of blowing fuse. Getting similar readings from the identical transistors is correct to expect. Looking again at Post #1, I see there are two Transformers in this amplifier?

[fuxxy]

Re: TOA BG-130 Amplifier power supply fuse blown

Look at the Output transistors...Yes the 4 on the big heatsink.....Each channel may have a complementary pair of NPN and PNP transistors.

Disclaimer: I've never been confident testing transistors with a multimeter

I've pulled all 4 transistors from the heatsink and board.
It looks like two complimentary pairs.
Facing the silkscreen on the front of the transistors, they are arranged like this

D2059 D2059 B1367 B1367

Not getting any shorts from any pins on each of the transistor, however, on "ohms" mode, I'm getting different values from the two B1367 transistors. I would have expected the two identical transistors to have identical results.

[Andrew F. Ali]

Re: TOA BG-130 Amplifier power supply fuse blown

Look at the Output transistors...Yes the 4 on the big heatsink.....Each channel may have a complementary pair of NPN and PNP transistors.

[fuxxy]

Re: TOA BG-130 Amplifier power supply fuse blown

Replaced F101 again
Plugged in transformer primary
Unplugged transformer secondary windings
Fuse stays intact, and secondary output is a steady 39.6v

[fuxxy]

Re: TOA BG-130 Amplifier power supply fuse blown

I'm at work at the moment, and don't have access. I'll disconnect the secondaries and see if the fuse shorts when I get home. I did test the rectifier, and I don't remember the forward voltage readings, but I do remember that all 4 individual diodes in the rectifier had roughly the same forward voltage and read open when tested in reverse polarity. All seems fine with the rectifier.

Can you identify the PCB markings for the output transistors? I'm assuming you're talking about the four attached to the big heatsink, but I'd like to be sure we're both looking at the same thing.

[R_J]

Re: TOA BG-130 Amplifier power supply fuse blown

Those resistance readings for the transformer are fine, I dought its the transformer at fault
I have a couple 110 to 20-0-20 the sec. res. is 1 ohm the primary is 3.5 ohms
You could check the output transistors (looks like 4 of them) and see if they are ok

[Andrew F. Ali]

Re: TOA BG-130 Amplifier power supply fuse blown

The transformer Primary windings are shorting. It should be near 100ohms or there about.

[budm]

Re: TOA BG-130 Amplifier power supply fuse blown

Replace the main AC fuse and disconnect the secondary side of the transformer so all you have is the AC feeding the primary side of the power transformer, if the fuse is blown again then you have bad power transformer.
You can also use a 40~60W lamp in place of the main AC fuse, it the lamp comes on and stays on brightly then you have bad transformer.
The DCR reading of the power transformer will show low resistance which is normal for power transformer.