Bugera 333 head (pre infinium) Blowing fuses

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Bugera 333 head (pre infinium) Blowing fuses

I have read some similar posts and responses that have been very helpful with troubleshooting this so far, but I am a little unsure of next steps, any help will be appreciated. I am a computer programmer/musician, not an electronic/amp technician, but have some familiarity and have usually managed to do my own repairs through the years.

Instantly Blows Fuses when flipping on power switch
Plug in - Does not blow fuse
Power on - Standby off - Blows fuses
Removed all Power tubes, still blows fuses
F1, F2, F3, F4 are all good
Disconnecting X26 2 - Gray wires, does not blow fuses

Reconnect X26 - 2 gray wires, and Disconnecting X16 Red Blue Brown wire, does not blow fuses,
will power on and stay powered on with standby on or off.

ReConnecting X16 Red Blue Brown wires, Blows Fuses
Still blows if X18 Red wire is connected or not
Still blows if X19 Brown wire is connected or not

I am pretty sure the output transformer is good, I tried it in another 333 and it works fine and when I tried the other amp's transformer in this amp, it still blew fuses exactly the same as this transformer.

I thought maybe it was the d1,d2,d3 or d4 diodes, and they are fairly inexpensive, so I thought about replacing all of them.
The schematic indicates that diodes D3 and D4 are R200F, and I was able to find those on mouser.
The schematic indicates that diodes D1 and D2 are 4007, and I am not sure where to find them, or what alternate parts, or values to look for.

Any ideas on what to check next, does this sound like the diodes, or something else I should check, I am not sure.

Thanks

[Jazz P Bass]

Do you have an ohmmeter?

If you 'think' a diode is bad, test it.

It sounds like D3 and/ or D4 are suspect. as they connect to B+, through the OT Red wire.

4007 diode is more properly identified as "1N4007".

Totally disconnect the OT (Blue, Red, Brown).
If the amp holds the fuse, measure the OT Red wire with respect to chassis/ Ground.
That is your Volts dc B+ voltage.
If it is good, do not bother replacing the 1N4007 diodes.

[DrGonz78]

I thought maybe it was the d1,d2,d3 or d4 diodes, and they are fairly inexpensive, so I thought about replacing all of them.
The schematic indicates that diodes D3 and D4 are R200F, and I was able to find those on mouser.
The schematic indicates that diodes D1 and D2 are 4007, and I am not sure where to find them, or what alternate parts, or values to look for.

Any ideas on what to check next, does this sound like the diodes, or something else I should check, I am not sure.

Thanks

Do you have a multimeter that has a diode checking feature or even just an ohms meter? Before just pulling out and replacing any parts it would be best to test those diodes to check them first. The R200F are fast recovery diodes and the 1N4007 are just plain old general purpose types (1000v). Here is a link to a thread talking about the fast recovery diodes.
http://music-electronics-forum.com/t41706/

Also here is a link to 1N4007 diodes on mouser. These are so common that you will even find them at Radio sHack.
http://www.mouser.com/ProductDetail/...ErRxax7Q%3D%3D

Remember though that is best to test the parts and confirm they are truly bad.

Edit: Jazz posted while I was typing but is much quicker than I.

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Yes, I have an ohmmeter, and used it to check the power tube sockets pin 3 for short to ground as mentioned in some similar post, they checked out OK.

Can I effectively check the diodes in circuit without unsoldering them?

[123]

Thanks for the advice ad links.

I went ahead and measured the diodes, still in circuit, not unsoldered at all. Not sure if this is the way to check the diodes.
I got these readings on my meter with the diode test selected.
D1 showed 660 on one side and 1 on the other side.
D2 showed 664 on one side and 1 on the other side.
D3 showed 525 on one side and 431 on the other side.
D4 showed 458 on one side and 380 on the other side.
Can unsolder one end and remeasure if I should.

Reading through the YBA -1 thread now.

[DrGonz78]

From your measurements it appears that those Diodes test good. At this point try to avoid removing components until certain that you must. That way we don't risk damaging the circuit board. However, when in question you only need to desolder one leg of those diodes to remove them from the circuit.

Instantly Blows Fuses when flipping on power switch
Plug in - Does not blow fuse
Power on - Standby off - Blows fuses
Removed all Power tubes, still blows fuses
F1, F2, F3, F4 are all good
Disconnecting X26 2 - Gray wires, does not blow fuses

Reconnect X26 - 2 gray wires, and Disconnecting X16 Red Blue Brown wire, does not blow fuses,
will power on and stay powered on with standby on or off.

ReConnecting X16 Red Blue Brown wires, Blows Fuses
Still blows if X18 Red wire is connected or not
Still blows if X19 Brown wire is connected or not

Let's first clarify which fuse or fuse(s) are blowing. You say Fuses which means more than one. The F1 fuse in this case is the 2amp B+ HT fuse. From what I am gather is that you said F1-F4 are all good. So the fuse that is blowing is the main power AC fuse? If that is the case what type of rating is that fuse? I attached the AC mains input board which has F1 as the primary fuse.

Edit: It might be time to build a light bulb limiter so we don't just keep blowing fuses. Search the web and read about that here>>>>
http://www.ssguitar.com/index.php?topic=2093.0

[123]

From your measurements it appears that those Diodes test good. At this point try to avoid removing components until certain that you must. That way we don't risk damaging the circuit board. However, when in question you only need to desolder one leg of those diodes to remove them from the circuit.



Let's first clarify which fuse or fuse(s) are blowing. You say Fuses which means more than one. The F1 fuse in this case is the 2amp B+ HT fuse. From what I am gather is that you said F1-F4 are all good. So the fuse that is blowing is the main power AC fuse? If that is the case what type of rating is that fuse? I attached the AC mains input board which has F1 as the primary fuse.

Edit: It might be time to build a light bulb limiter so we don't just keep blowing fuses. Search the web and read about that here>>>>
Light Bulb Limiter

That sounds like good news on the diodes, I was not looking forward to having to unsolder and resolder them, for the reasons you mention.

Yes, the only fuse blowing is the main power fuse, it is a slow blow ceramic 5x20 mm 3.15 amp
250 volt fuse.

OK, I will look in to the light bulb limiter.

[g1]

I got these readings on my meter with the diode test selected.
D1 showed 660 on one side and 1 on the other side.
D2 showed 664 on one side and 1 on the other side.
D3 showed 525 on one side and 431 on the other side.
D4 showed 458 on one side and 380 on the other side.

From your measurements it appears that those Diodes test good.

I was expecting D3 & D4 to measure '1' or 'OL' or something high one way, so I suspect them. Were you doing the diode check with one probe at each end of the diode, then reversing the leads?
DrGonz, am I missing something?

[Jazz P Bass]

Looks to me as if D3/D4 are conducting both ways.

Ouch.

[Enzo]

Are you putting your meter probes on the two ends of each diode? That is the right way, then reverse teh probes end for end. I may be wrong, but it looked to me like you were taking readings to ground from each end of the diodes. That is not a valid test.

[123]

Are you putting your meter probes on the two ends of each diode? That is the right way, then reverse teh probes end for end. I may be wrong, but it looked to me like you were taking readings to ground from each end of the diodes. That is not a valid test.

I was a little uncertain about the proper way to perform the diode test. I had read a few different ways to do them.

For my readings, the diodes were still in circuit. I touched one meter lead as close as possible to the input side of the diode, and the other lead as close as possible to the output side of the diode. I recorded those values. Then I reverse the red and black leads, putting them once again as close as possible to the diode input and output side, and recorded those values.

If I did this incorrectly, or there is an alternate way to do this, just let me know I will do it again, I am very thankful for all contributors time and knowledge, I am unsure at this point.

[123]

Looks to me as if D3/D4 are conducting both ways.

Ouch.

That is what I was curious about, and made me suspicious that D3/D4 needed replacing. But, I would defer to the forums general consensus though.

[Enzo]

Diodes are dirt cheap, if you need to replace two of them, just replace all four.

[DrGonz78]

I was expecting D3 & D4 to measure '1' or 'OL' or something high one way, so I suspect them. Were you doing the diode check with one probe at each end of the diode, then reversing the leads?
DrGonz, am I missing something?

I was thinking that those diodes were in parallel to other components and that many times you get some funky readings. In this case yes pop a leg up and check it out of circuit. However, I must have been fixated on those flybacks and jumped the gun.

[g1]

Definitely you need to at least lift one end of each and recheck D3 & D4.