No name Vintage guitar amp

[J M Fahey]

Looks very clean inside, clearly has been refurbished not too long go.

Yes, follow suggestions above.

Somewhat surprised at the "small" 640 x 480 image posted, no modern phone takes such small ones, maybe you asked imgbb to downsize it to that resolution?

I would repost original phone picture but asking imgbb not to reduce - optimize resize original picture, just upload it as is, no changes, no fitting to anything.

So we can read parts values, etc.

[Mick Bailey]

The death cap connects one side of the incoming mains to ground. From what I can see, there appears to be a capacitor connected between the fuse holder and chassis ground. Please correct me if I'm wrong.

The only cap rated to fail open is a Class Y type. Any other can fail short.

[tonyw7]

Thanks Mick
I will replace that cap with a class Y. What size micro farad should I use?

[Mick Bailey]

You still wouldn't have the protection that an earthed chassis provides in the event of a serious fault situation. I don't advocate leaving an amp with a 2-core cable regardless of the cap type. The reason for mentioning a class Y cap was to identify this as a type of cap that fails open, compared to others which can fail either way. Getting rid of the cap and installing a 3-core cable with a dedicated earth connection that's not shared with any other chassis ground gives a safer amp.

[Chuck H]

...

[Helmholtz]

AFAIK, a transformer bolt is not considered reliable enough for safety earth connection.

[Chuck H]

AFAIK, a transformer bolt is not considered reliable enough for safety earth connection.

No. It's not. The safety ground should be a dedicated connection involving drilling, a nut and bolt, a crimp connector ring, a tooth washer and ideally some heavy viscosity temperature stable anti oxidant grease. And the ground conductor on the AC cord should be longer than the AC leads to ensure it is the last to become disconnected if the cord is forcibly pulled out.

My illustration above is meant to indicate where that loose ring connector is intended to be. It's intended to be under a transformer bolt contacting the chassis.

[Mick Bailey]

The ring terminal looks to be the ground point for the transformer centre taps. Its unclear from the picture whether its bolted to the chassis - if so it can stay there and the the cap just snipped. There looks to be the flats of a nut, so it may be OK. In any case, the mains chassis earth should be on its own bolt.

I'd rather not ground anything to a transformer bolt as they can loosen over time due to vibration and heat cycling and sometimes have insulating washers that compress.

[tonyw7]

The ring connector is floating because I was in the process of removing the blown power transformer., I will install a 3wire power cord and replace the cap with a class Y.

[g1]

If you deem the cap necessary, then yes, class-Y is the way to go. It seems some modern manufacturers are using them from line to chassis, for what I assume to be RFI related reasons. I've never run into any issues by just removing them altogether.

[Chuck H]

Well, to speak plain on the matter...

If the amp were absolutely original and had it's original two conductor AC cord there could be an argument made for collectibility in keeping the two conductor AC cord. And this would be contingent on the ideal that the amp wouldn't actually be used much if at all. Since none of this is the case I'm of the firm opinion that for best practice and safety reasons a three conductor grounded AC cord should be installed. It will cost you the price of an AC cord. A marginal difference compared to sourcing and installing the suggested capacitor.

I'm sure I'm not alone saying that I've been hit with a hot chassis more than once. It happens. It's Russian Roulette as to when it's a bigger problem than just getting zapped instead of dead. An earthed chassis can't do this and the implementation is easy. Any reason for not installing a three conductor AC cord and grounding that amp chassis is absolutely flawed.

No reason to install the "death cap" even with a Y spec part.

[Mick Bailey]

Agreed.

I've never found a situation with a vintage amp where I had any reason to keep/replace that cap. Eliminate it and you don't have a situation in the future where it fails and someone replaces it with an orange drop or similar. The OP should appreciate what happened to ths amp - a safety-critical cap got replaced with one of the incorrect type just because there was a cap there in the first place.

Maybe a museum amp kept for reference would be a different situation, but any amp in use needs to be safe.