Gallien-Krueger 800RB

[Janky]

So, I celebrated early. Damage was in fact done to the Transformer...I'm back to looking at the toroidal kit.

[J M Fahey]

Ouch!!
Exactly what kind of damage?
What are the symptoms?


By the way:

on the other side of the switch, I get continuity!

is not enough for a clean bill of health.

[Janky]

Ouch!!
Exactly what kind of damage?
What are the symptoms?


By the way: is not enough for a clean bill of health.

The thermal switch having been at 121° c was obviously not low enough to prevent the PT from frying. When I threw the switch it made some unsettling sounds and the lights in the room dimmed. So yeah. Instantly killed it. New one on order.

[The Dude]

Have you tried it with the secondary disconnected? The transformer may have survived (sans thermal fuse) and you have shorted rectifier(s), output transistors, or something of the sort.

[52 Bill]

When I threw the switch it made some unsettling sounds and the lights in the room dimmed.

What size fuse did you use in the amp?

[The Dude]

The fuse rating will be underneath the tinfoil.

[Janky]

The fuse rating will be underneath the tinfoil.

Oh Jeez...lol. I see the room's turning on me!
The original fuse is still there, un-blown..

[The Dude]

I was just kidding. That said, you may want to verify that it's the correct value. If the lights dimmed before the fuse blew, it may be over fused.

[J M Fahey]

Ok, now just answer a simple multiple choice test.

Describe what's inside the fuse holder.

Pick one or more if applicable:

1) a 20-30A fuse, pulled from a car or bike (Harley Davidson class, not a moped)

2) a 2-4A fuse, wrapped in tin foil

3) a penny nail

4) wrapped roll of tinfoil, no fuse inside

5) a .22LR live round

6) a #8 standard blasting detonator

7) an AWG#6 straight wire, cut so it touches necessary contacts

8) nothing (fuse holder empty) , but wires leading to it cut, ends stripped and twisted, with or without a piece of tape around them ("without" adds bonus points)

9) some new creative kludge we can't even imagine (again: extra points)

[Leo_Gnardo]

Oh Jeez...lol. I see the room's turning on me!
The original fuse is still there, un-blown..

Comes a point in some shows where that happens. Heck even at the New Hampshire debate... but that's another thread.

Why I mentioned, the dim bulb tester... if you just plug 'er straight in & ALL the lights in the room go dim, well that's what we were trying to avoid.

It's time to think about your commitment to this fine old but now disheveled piece of gear. You know it's going to take a new PT but then what after that? A lot of time and expense perhaps when you could buy a good used 800RB for relatively cheap. That is, if your heart was set on owning one.

Some probing of power supply rectifier & output transistors is in order, see whether you measure one shorted transistor after another. If so, that good used 800 starts looking more & more attractive. Unless you're committed to developing your SS amp fixit chops with this one. You'll have to de solder power transistor emitter & base pins from the circus board to test 'em individually, the task becomes more difficult the deeper we go.

[The Dude]

I have 2 of them. They're worth it.

[rjb]

Failing that, would some helpful MEFster please post a link to the MEF light bulb limiter sticky.

Don't know about no sticky, but here's another source.
Sorry I may have shown up too late to be a helpful MEFster.
On the plus side, the assembly diagram would make a great tee shirt.
Powering Your Radio Safely With a Dim-bulb Tester

[Leo_Gnardo]

Don't know about no sticky, but here's another source.
Sorry I may have shown up too late to be a helpful MEFster.
On the plus side, the assembly diagram would make a great tee shirt.

Yup, like that, and plenty helpful thanx! When building, one should pass a ground wire thru from AC plug to test socket for safety's sake.

I use mine rarely but it does come in handy. Why rarely? I'm lucky enough to have a variac, a clamp-on ammeter, and a special short extension cord with outer insulation removed - put the clamp-on on the hot lead, dial up slow on the variac while monitoring current, if anything's out of sorts it shows up fast. Short of having this kind of rig, the dim bulb does the trick, cheap. Also there's some things that you can't sneak power up on like SMPS powered gear, then it's dim bulb time, it suits me fine.

Tee shirt for nerdy techs, sort of a way of saying "I'm with (dim bulb)."

[J M Fahey]

Old but (sigh!!) true