Peavey 6505+ DC Heater question

[Steelwitch]

I have a Peavey 6505+ up on the bench with intermittent AC heater supply due to a bad connection in the spade connector. My plan is to replace the spade connectors with turrets for a better connection. I have read that the rectifier for the DC heater supply (in4003 at 1A) is way under spec for the current rating and fail often. I’m looking to replace them with a 3-5A diode that will fit onto the board. Any suggestions?

I have had a few people recommend using a 10A bridge rectifier mounted to the chassis between the PT and circuit board, but my customer would prefer to keep the cost down so I’m looking for other options. Thanks!!

[Jon Snell]

The rectifier gets hot and fails, a set of 3A 1n540*, (* meaning any of the range), mounted off the board so there is at least an air space between the diodes and the pcb. I usually form a spring shape with the leads, that helps to dissipate the heat.
Replace the spades with whatever you think but I would recommend, replacing the tags and soldering the wires to them. Something else that is less likely to fail in the future.)

[Steelwitch]

The rectifier gets hot and fails, a set of 3A 1n540*, (* meaning any of the range), mounted off the board so there is at least an air space between the diodes and the pcb. I usually form a spring shape with the leads, that helps to dissipate the heat.
Replace the spades with whatever you think but I would recommend, replacing the tags and soldering the wires to them. Something else that is less likely to fail in the future.)

Can you clarify what you mean by replacing the tags? Do you mean soldering directly to the connector?

I really like the spring shape idea. Do you have any pics? Interested to know how you get a tight coil on the component leg

[Jon Snell]

Yes, remove the connector on the wire end and solder directly to the tag. I have never had them burn out though.
I get a component and wrap the leg around a small phillips screwdriver blade.
I then adjust the turns to the required shape to fit the pcb holes or tag strip.

[Enzo]

The 6vAC heater connectors are under spec and burn up. SOlder the wires directly.

I never encountered rectifier failure, the load on each supply is just 150ma for tube heaters. Add a few milliamps for the couple relays.

[Steelwitch]

Cool, I’m still trying to figure out if turrets will be the best way, since there’s two pads for each terminal I may drill out one of them on each transformer side and route the wires through Marshall style for strain relief and solder directly through to the pad. Maybe it’s not needed. I don’t love the idea of soldering directly to the terminals though!

[Steelwitch]

Just ordered some in5408’s for the DC heater supply. I haven’t gotten one where the rectifier burnt up but there are plenty of threads with issues like that, so I’m just gonna go ahead and do it, it’s less time for me to do it while it’s here than to come back later when it’s smoked

[Jon Snell]

I have had four in for repair with destroyed diodes and bad contacts on the spade connectors but many more that didn't fail. I replaced the diodes and connectors anyway as I was in there replacing the swollen capacitors, belt and braces.
Mounting them away from the board also helps and you will never see that amplifier in again for the same fault.
A 1N4002 is fine but the 1N540* series is more reliable.

[Helmholtz]

With 1N400x diodes in power applications always use the glass-passivated (GP) types. These have much better long time reliability/lower failure rates (FIT values) than the cheaper standard versions.

In one of my former products (a kind of SMPS) the calculated mean time to failure (MTTF) could be increased by a factor 10 using GP type 1N4007 rectifiers.

[Jon Snell]

Nothing wrong with soldering to the terminals, as long as the pad on the pcboard has not been damaged.
It is the poor crimping on the connector that is the problem so new connectors will fix it as well, if you have a professional crimp tool that has a force of a couple of tons that is.

[Danglin' Fury]

I just had a 6505+ 112 combo on the bench with a bad DC heater circuit... it was a shot rectifier diode...1N4002 diodes I think....I replaced them with 1N4004 diodes and I clipped off the spade space connectors and hard soldered them to the board....no worries now...

[Steelwitch]

Nothing wrong with soldering to the terminals, as long as the pad on the pcboard has not been damaged.
It is the poor crimping on the connector that is the problem so new connectors will fix it as well, if you have a professional crimp tool that has a force of a couple of tons that is.

I don’t have a crimp tool but I should! The stuff I have crimped I did with rounded needle nose pliers strategically. I’d probably be more confident that I can crimp something better than peavey if I had a better tool 🤔

Anyway, still waiting on these diodes since it’s the end times, I’m glad I could even get them. Good to know the DC heater rectifier is a persistent issue and that IN5408 was the right way to go. I was tempted to find a 10A diode but there’s probably no way to fit them on the board. Would have to be a bridge rectifier mounted to the chassis between the transformer and circuit board.

Peavey had the right idea with their Classic 212 models, those things never smoke all on their own. PTP output section and everything. Really nice stuff.

[The Dude]

If you don't have a crimp tool, it also works to flow solder into the crimp connector around the wire. I'll often do that, even after crimping, for a little insurance.

[Steelwitch]

After handwiring everything in, and replacing the DCH rectifier with IN5408, to my amazement: the AC heater supply is still intermittent. I’m reading 3.5v on one lead, 0v on the other. When it does come on, I can see 7v on the winding that is supplying voltage and 0 on the other. A bit confused by this. I guess the PT is faulty? What’s a way to know for sure? Reading .4ohms between the leads of the AC heater, and the rest of the circuit looks normal. Not getting AC voltage of any kind to either output tubes or the PI, which probably means no current

[HaroldBrooks]

With 1N400x diodes in power applications always use the glass-passivated (GP) types. These have much better long time reliability/lower failure rates (FIT values) than the cheaper standard versions.

In one of my former products (a kind of SMPS) the calculated mean time to failure (MTTF) could be increased by a factor 10 using GP type 1N4007 rectifiers.

Hi Helmoltz,

Can you explain to me the difference between glass-passivated (GP) types and any other 1N4007 diodes ? How do I spot the differences when someone is selling them over the internet ?

I didn't realize there was any difference, but I want to be on the lookout for the "Better" type next time I purchase them.

Thanks for the help.