Yamaha Bass Amplifier

[Bobhoskin]

Here I am with a Yamaha F 20B Bass Amplifier
a day I plug it in and found it dead, with smell of burn.

Open up, I found the IC (the one on the dissy) was burn... on it I can read TDA2030 with a final letter that seems an "A".
Then the fuse was dead.

I order the TDA2030A and change it, the fuse too, plug in, button to ON, and after 2 sec. the fuse will blow up.

What can I try to check?
Maybe the TDA2030 final letter is not an "A"? ....and so what are the differences of the final letters?






The WHITE and RED cables are to the Speaker
The RED and YELLOW are to the power switch button
The 5 cables that goes to the IC TDA2030 are all straight.

I didn't test anything else, where I start?

Please, help!

[budm]

Re: Yamaha Bass Amplifier

Check the bridge rectifier DS1?? (black rectangular) by the two large filter caps.

[Bobhoskin]

Re: Yamaha Bass Amplifier

Check the bridge rectifier DS1?? (black rectangular) by the two large filter caps.

The rectifier is a D2SBA - 20
I set the multimeter at 2000 ohm, I get readings in all combinations with positive to the right and negative to the left of all terminals (all 574ohm) except the two in the center gives no reading.

Testing in the opposite side, I don't get any reading.... but if I set the Ohms to 20k, I get readings in all directions (about 15.40 kohm) except the first and last terminals gives about 6 kohm. Same the 2 in center gives no reading.

It's better to remove the Bridge rectifier to test it?

[budm]

Re: Yamaha Bass Amplifier

yes

[Bobhoskin]

Re: Yamaha Bass Amplifier

yes

Ok, I understand how it works,
out of board, terminals:
2-1, 3-1, 4-1, 4-2, 4-3 reads ok (574ohm) except 4-1 gives about double ohms.
of course 2-2 gets no reading in both direction.
all other directions, no readings.
It's a good bridge rect., right?

What can I try doing now?

[selldoor]

Re: Yamaha Bass Amplifier

It seems ok.
I dont know why this test always gets so complicated,
a) put your multimeter in diode test mode
b) put your black lead on + and the red lead on the adjacent ~ record reading
c) reverse the leads - recording reading
d) put your black lead on - and the red lead on the adjacent ~ record reading
e) reverse the leads - recording reading

Each pair +~ and ~- is like a diode

A good diode should read 0.4V to 0.7V in one direction and 0L in the other.

[Bobhoskin]

Re: Yamaha Bass Amplifier

I'm in doubt with the last letter of the TDA2030, because it's in melted condition.... here to pics:
Seems like a "M", if it's an "A" strange it's without the middle - (like a V upside down)

[Bobhoskin]

Re: Yamaha Bass Amplifier

It seems ok.
I dont know why this test always gets so complicated,
a) put your multimeter in diode test mode
b) put your black lead on + and the red lead on the adjacent ~ record reading
c) reverse the leads - recording reading
d) put your black lead on - and the red lead on the adjacent ~ record reading
e) reverse the leads - recording reading

Each pair +~ and ~- is like a diode

A good diode should read 0.4V to 0.7V in one direction and 0L in the other.

Thank you Selldoor,
I confirm:
b) 574 ohm
c) no reading
d) no reading
e) 574 ohm

[selldoor]

Re: Yamaha Bass Amplifier

Some members would prefer it if you just posted the pictures as attachments
and not inline.

What is a dissy? Is the TDA2030 on the end of the short extension?
If so in the first lot of pics is that the new one.

The one in the last picture appears to have a plastic washer on?
When you tried the new one did you have it back in the frame/box - was the
new ic screwed down and if so did it have the plastic washer in place to keep it isolated?.
Try gently cleaning the burnt one with some isopropyl alcohol - may improve the letters.

EDIT - Forgot to ask - does the fuse blow if you switch it on with the ic unplugged

[midibob]

Re: Yamaha Bass Amplifier

Hi,

The TDA2030A is the higher power version.

I would check the power + and - to ground without the IC connected as has already been mentioned. Can't find a schematic but it's probably +/-15v. Also make sure your speaker hasn't gone short cct. Unlikely, but you never say never!

Good luck
Midibob

[Bobhoskin]

Re: Yamaha Bass Amplifier

Some members would prefer it if you just posted the pictures as attachments
and not inline.
What is a dissy? Is the TDA2030 on the end of the short extension?
If so in the first lot of pics is that the new one.

The one in the last picture appears to have a plastic washer on?
When you tried the new one did you have it back in the frame/box - was the
new ic screwed down and if so did it have the plastic washer in place to keep it isolated?.
Try gently cleaning the burnt one with some isopropyl alcohol - may improve the letters.

EDIT - Forgot to ask - does the fuse blow if you switch it on with the ic unplugged

Ok, I'll just attach picture next.
Dissy, sorry I mean the heatsink. Yes, the TDA2030A is on the end of the extension and it's the new one.
I think you found the possible problem, because I try it mounted on the box without the plastic washer on it.
Tomorrow morning I try and let you know, thank you (you have good eyes )

Hi,

The TDA2030A is the higher power version.
I would check the power + and - to ground without the IC connected as has already been mentioned. Can't find a schematic but it's probably +/-15v. Also make sure your speaker hasn't gone short cct. Unlikely, but you never say never!
Good luck
Midibob

Hi Midibob,
If can help, I just test yesterday the transformer unplugged from the board, and gives about 14,5V ~
Tomorrow I'll check the speaker too.

[mariushm]

Re: Yamaha Bass Amplifier

https://cdn.badcaps-static.com/pdfs/...176bf5b432.pdf

The tab is attached to pin3 of the chip (-Vs) and the case is most likely ground, so you have to isolate the chip from the case with the plastic ring and some insulating thermal material (a pad or something) between it and the metal of the case.

[Bobhoskin]

Re: Yamaha Bass Amplifier

Thank you again Selldoor,
you have good eyes and intuition, I forgot to put the plastic washer,
now it's working all perfect.

[yamahahead]

Re: Yamaha Bass Amplifier

Hello everyone!
I'm new here.
I need your help with this.
I just recently bought YAMAHA SR400B bass head amplifier. Does anyone have any idea the true WATTS of this amp, is it 400 or 265? Mostly amp wattage are patterned with the model.

thanks!