Peavey BH400 Problems

[Techknowman]

On an ending note, The 39095750 OTA adaptor assembly that I got from Peavey worked well.
It replaces the peavey 87478 or 787478. I did reverse engineer it to see what makes it tick so I have a schematic of it should someone want to make there own.
However, the $15 peavey charges for the unit is a good deal.
It comes with an 8 pin plug to plug into the existing socket. The PCB has a 2 channel OTA chip. only one channel is used. the other is set for unity gain and is basicly disabled.
I'm sure this was done to prevent noise.

[Enzo]

And I ask you, what other company besides Peavey would go to the trouble to make up a little work-around board like that to replace an obsolete IC used in their models from 20 years ago? Not one that I can think of. I love those guys.

[Techknowman]

I have to agree with you Enzo. That means a lot to anyone that services things. Even if all they provided was a schematic and the raw part numbers, that’s way better than a lot of companies do!
Hell some make it a downright pain to even deal with them. Getting Schematics ect.
I sometimes want to tell the customer to take those and pitch it in the garbage and buy a real companies equipment!
Dealing with Peavey was no pain at all, I told them I needed a part, they told me its obsolete this is the replacement part number, they were out at that location but they got them from another location and in my hands in a decent amount of time. No questions, issues or drama. No questions whether I'm qualified, (which is debatable lol) or requirements for me to fill out some form or disclaimer.

[km6xz]

Peavey is a pleasure to deal with.....if you live in the US but if not, you have no support and no one in the company cares at all. There seems to be no oversight of their international distributors who are trashing their reputation in many parts of the world. This is one reason the future for US based companies is really bleak, not knowing or understanding the rest of the world means companies who do, will crush them eventually. They lose more sales world wide due to bad customer service than the market in the US can overcome. Look how badly the US car and computer companies dealt with international markets and lost them. Even the record industry was so USA-centric that even the most general appeal labels never moved out of the local market and instead licensed recording to foreign distributors, as an afterthought and which generated almost no income for artists in royalties. All those companies have foreign control now because of ignoring the rest of the world.
You will not find the foreign based manufacturers failing to know markets outside their own country.

There has been a run of CA3080ae chips using the original artwork from Intersil but the only place I have seen where you can buy one or two and not a stock is Small Bear. But any new design has great options available with much better parts from That Corp, TI or AD that are cheap, a lot quieter, lower distortion and more stable. Not so many in DIP-8 form but those who want to design using SMD have all the best options for lower prices.

[Emanuele]

Hi,I'm new to this forum and I had to resurrect this thread since I got similar problems but I can't sort them out..

I bought a broken markIII, found that one of the power transistors was busted so I bought eight new ones..changed those, fired it up , BIG hum and R61 burned.
So I checked Q2 and Q12, they seemed fine but I changed those anyway since they're so cheap..fired it up again and guess what? R61 burned again.

What should I check now? Diodes around drivers? The small transistors before drivers?

Thanks,

Ciao!

Emanuele.

[Enzo]

Hi Emanuele, welcome to the forum.

Really, we'd much prefer you start a new thread for your amp. it gets confusing having more than one amp in a thread.

Are we sure your MK3 amp has a 400BH not a 400B/G?

Assuming 400BH, why are we starting with small parts. When you changed the power transistors, did any of their cases get shorted to chassis? measure the cases of each to chassis and see fi there is continuity to any - there should not be.

I don't think it is possible, but any chance one of the three wire cables from the main board to the power transistor board is connected wrong?

Your BIG hum is likely DC on the speaker (the cone moves one direction and stays there) DO not connect ANY load to the amp until it is stable and working. Check for DC on the speaker wires.

The only path for current through R61 is Q14. So either it is shorted or something is turning it on hard.

[J M Fahey]

And build lamp bulb limiter first of all and plug your amp there *always* until amp is fixed.

[Emanuele]

Hi Emanuele, welcome to the forum.

Really, we'd much prefer you start a new thread for your amp. it gets confusing having more than one amp in a thread.

Are we sure your MK3 amp has a 400BH not a 400B/G?

Assuming 400BH, why are we starting with small parts. When you changed the power transistors, did any of their cases get shorted to chassis? measure the cases of each to chassis and see fi there is continuity to any - there should not be.

I don't think it is possible, but any chance one of the three wire cables from the main board to the power transistor board is connected wrong?

Your BIG hum is likely DC on the speaker (the cone moves one direction and stays there) DO not connect ANY load to the amp until it is stable and working. Check for DC on the speaker wires.

The only path for current through R61 is Q14. So either it is shorted or something is turning it on hard.

Ok , I'll open a new topic as soon as I check the sockets, and other stuff..thanks for the fast reply