Question about rectifier valve solid state replacement in an Ampeg B15

[chrisaxe]

Hello,

I was just wondering if someone here can explain the situation I am in. So I have a 1970 Ampeg B15. Works brilliantly. When I bought it, it had a rather dodgy looking homemade solid state rectifier that someone had fashioned out of a couple of diodes and an old valve socket. It worked fine, but I was advised by a tech so either swap it out for a proper solid state rectifier, or switch back to a valve rectifier - the logic being that they should be interchangeable as the rest of the amp had not been modified in any way, and the exposed diodes could be dangerous.

So, I bought both a solid state rectifier ([url="http://www.hotroxuk.com/solid-state-rectifier-ssr.html"]http://www.hotroxuk.com/solid-state-rectifier-ssr.html[/url]) and a 5AR4 Valve ([url="http://www.hotroxuk.com/tad-gz34-5ar4-str-premium-select-rt501.html"]http://www.hotroxuk.com/tad-gz34-5ar4-str-premium-select-rt501.html[/url])

The solid state works perfectly and sounds great, but the valve does nothing - the amp is just silent. I sent back to valve to HotRox to have it tested, and it came back fine. It is a fully working valve.

So my question is, any idea why I get no sound from the when using the rectifier valve?

Many thanks in advance,

Chris.

[ColinB]

Has the previous owner disconnected the heater wires?

[chrisaxe]

[quote name='ColinB' timestamp='1472837697' post='3124703']
Has the previous owner disconnected the heater wires?
[/quote]

I have no idea - is this something I can easily check or a job for a tech?

[Beer of the Bass]

[quote name='chrisaxe' timestamp='1472840706' post='3124747']


I have no idea - is this something I can easily check or a job for a tech?
[/quote]

Does the rectifier valve glow? That would be the simplest way to check.

[Passinwind]

[quote name='Beer of the Bass' timestamp='1472848401' post='3124849']
Does the rectifier valve glow? That would be the simplest way to check.
[/quote]

Yep. That sounds very likely to be the problem, unless the filament supply has croaked on its own, which could have been the impetus for using the SS sub.

[chrisaxe]

No glow - that must be what it is then. Thanks all.

[Beer of the Bass]

Like Passinwind says, It could either be that the heater wires to the rectifier socket have been disconnected, or the 5V winding on the power transformer which supplies them has stopped working. If it's the latter, your choices would be to stick with the SS rectifier or have the power transformer replaced or rewound.

[luckydog]

[quote name='Beer of the Bass' timestamp='1472891879' post='3125064']
Like Passinwind says, It could either be that the heater wires to the rectifier socket have been disconnected, or the 5V winding on the power transformer which supplies them has stopped working. If it's the latter, your choices would be to stick with the SS rectifier or have the power transformer replaced or rewound.
[/quote]

Yes I agree with the diagnosis. The heater is a separate winding on the transformer and has a peaceful enough life, very unusual for a transformer to fail like that without cause. More likely it's a dodgy connection, perhaps the socket, solder connections, or even at the joint between wiring and the transformer inside the transformer wraps?

Being an isolated 5V winding, if it is the transformer then a small extra toroidal transformer mounted under the chassis would save changing/rewinding it ?

None of this is DIY though, definitely ! just for info.

IMO the valve rectifier is worth restoring, and the amp is obviously well worth preserving. Lovely amp.

LD

[chrisaxe]

Thanks everyone, appreciate the help. And I agree - worth restoring such a great amp.