Gibson Skylark(GA-5) 1960 filter cap.

[Normster]

Scratchy pot may be a bad cap...likely the cool looking bumble bee connected to the pot. Check for DC voltage. If present, replace the cap.

[Bigbear]

Thanks for the tip on checking for DC,can I do this using just a DMM?????
Cheers,Bigbear.

[Bigbear]

Hi,
I've measured DC on the right lug(looking at back of vol pot),it measures 8.65v at min volume and 2.58v at max volume.
Does this suggest dodgy cap??
Cheers,Bigbear.

Also got DC on the middle lug 2.70v at max vol, 0v at min vol.

[Phil_S]

Caps block DC. Leaky caps don't block. Check for DCV across the cap. Your DMM is the right tool. It sounds like that cap needs to be changed. The schematic shows it is .02/400v. You are OK with .022, which is a common value. I don't think this amp is going to be picky about what type of cap, but I'd avoid ceramic. Get some kind of poly-film and don't spend a lot of money. There are audiophool caps out there that do things no one can hear.

[Bigbear]

Just a word to say thanks guys,
Replaced cap with a little yellow vishay 630v 22nf and all pot scratching is gone......this little guy is good to go!!!
Unbelievable how quiet this thing is even with single coils(standing at the right angle of course!)
Hard to think what I paid for this guy and all it took to get it up and running!!!!
Many THANKS again for your help and wise words of wisdom,especially Phil.
Cheers,Bigbear.

[Phil_S]

Thanks, but I did the easy stuff. I think the gold ring goes to Norm, who got the scratchy cap.

[norris2002]

Just out of interest, what car boots are you going to in the UK to pick up things like this, and how much did you pay, if you dont mind my asking?

Neil.

[LonnieWest]

Hello everyone.

I have a 1962 Gibson Skylark GA-5 that is very similar to the amp that started this thread. The amp was purchased new in 1962 and used for about a year before going into storage. It's been in storage until March of this year.

It is in amazing condition! However, it does have a loud 60hz hum.

I've done electronics work for years, so I know what to do to fix it, but I'm not really interested in keeping this amp. I'm looking to sell it.

So my question is this: is an amp this age worth more in "original" condition (it even has the original schematic and spare fuse inside it!), or in working condition?

I can definitely re-do the electronics so it sounds great, but does that reduce it's value as a collector's item?

[orrong65]

A great build story Bigbear - but just a note of caution on stepdown transformers:

I'm in a similar position to you here in Aus with 240v wall voltage. Stepdowns are great because you can get an accurate 110V, unlike many of our friends in the US at present.

But the problem is that most stepdown transformers here are insulated or double insulated (double square symbol - Class II) as they are primarily made for power tools/chargers. This means they have no direct earth coupling from the wall socket to the stepdown output, even if it is a 3 pin socket.

Not the best situation for a guitar amp, with the player connected to the metal of the guitar strings.

So we only use stepdowns with a direct earth pass-through. Easy to test for. Better to be safe than to be burnt.

[Structo]

@ Lonniewest,

I think hard core collectors want the amp to be all original, right down to the bad caps.

But it has been long held that maintanence and safety items like adding a three prong cord, removing the "death cap" and replacing all electrolytic caps are acceptable.

If you are real crafty, I've seen guys gut the old caps and install the new ones inside the old shell, and sealing the ends.
That way they still look original but are in fact brand new and hum free.

[Phil_S]

+1 on what Structo says. I think eBay value is more than $300, less than $500. Who knows, maybe such a minty looking one will go for more. I wouldn't do anything at all to it. You won't get your money out of it, and the new owner may have different ideas about what should be done. IMO "all original" will bring you the best price. People who buy these things should know what it's going to need. Disclosing the hum is present will make you look honest, as it is to be expected. Not saying anything about it would probably be the wrong thing to do.

[Cliff Schecht]

Yeah that amp would definitely be worth more untouched. But is there a big collectors market for these things?

[LonnieWest]

I have no idea if there is a market for these things or not, to be honest.

However, I am just not the kind of guy that likes to gold onto antique gear and give it the care and respect it earns. All the equipment I have, I use. I wouldn't feel right repairing this amp (and I thought the same thing about the cap... gut it and put new caps in the old case so it still looks original!) to play it, nor can I really justify having it around for show just because it's almost 50 years old.

I'd rather see it go to someone who is really into these things.

I guess I am just going to photograph and document it well, explain that it works but has a bad hum and needs the caps replaces, and put it in eBay to see what happens.

Thank you for the feedback everyone, I do appreciate it!

[noxea]

hi everyone,
thanks for all the feedback on this topic, it really helped me to repair my '59 GA5.
i got the amp with new power filter caps, but the amps started to sound weird after 20 minutes of playing. it also had a scratchy volume pot.
i replaced the two "bumblebee" coupling caps with reproduction ones made by Luxe.
the volume pot is like new and the amp sounds ... amazing.
thanks and enjoy these little amps !

[Gibsonman63]

deleted.