Custom 50 Combo Amp Repair Advice

[jinglejangle]

Hello All,

Wonderful forum - so glad it exists with such good advice!

I recently bought a Hiwatt Custom 50 SA112 (Serial: 14593) from Guitar Center (got a deal) and I'm pretty sure it needs the caps replaced among other repairs.

Rundown of the amp:

- Hylight, but PCB
- Original Fane speaker
- Partridge transformers
- A "two-holer"
- White jacks in the back plate
- Still has Mullard power tubes (Tung Sol pre)
- Really rusted corner where the ground attaches to the chassis
- Caps that have a small, but noticeable bulge
- Yellowish crud on the surface and interior of the amp. This residue covers almost all of the components on the inside of the amp. I'm thinking this is either from smoke, or oxidization of the chassis. I've read that yellow residues on metal surfaces can be Cadmium Oxide, which is a class 1 carcinogen.

A few questions:

1. If anyone is in the Miami area - know a good tech? I've ruled out Wycliff in Hallandale Beach and Steve from Sam Ash.
2. Are there any good places to get F&T (supposedly the standard...) caps that are compatible? From what I've read, these are 220uF 350V.
3. Is there a safe way to remove the yellow gunk?

I've been playing through a THD Hotplate and, probably unwisely, cranking the amp. Still sounds better than my Fender Bassbreaker, even when attenuated 16 db. The reason I'm cranking it is because I can't get a natural guitar tone without a little grit to add with a pedal. The problem, of course, is the tubes will wear out - just last night the volume randomly dropped and the amp made a scratchy noise at the same time. I hope it's the tubes because the amp is not in the best shape and I don't want to damage any circuits.

With that said, does anyone have any recommendations as far as overdrive/distortion pedals? Does anyone have any recommendations in regard to cranking the amp and getting a good tone in general?

Thank you!

[mhuss]

Sorry, I don't know any techs in Florida.

The yellow stuff does not look like Cadmium to me, more like the stuff left over from when an electrolytic explodes. Do all the caps look original (including those on the 'back' board)?

I've never seen a Hylight chassis with a plating problem.

--mark

[jinglejangle]

The caps do look original (all have the blue paint on the solder joints). There are no caps on the back board (if I understand the backboard to be the other side, where the tubes are mounted). Just side-mounted in the chassis. This is one of the last runs of Hylight era amps. Probably a 1981?

I wish I had a picture of the entire chassis. There is an area of really bad rust/oxidation in the corner. Someone must have dumped something in there, somehow (there's no indication of a spill anywhere else on the amp). The yellow crud is even on the outside of the amp, embedded in the tolex, I think. Maybe it's marijuana/cigarette residue?

I wouldn't have bought the amp if it was as expensive as the current going price - around $2000. I got it for $1,100 after tax. I would rather have bought a Hi-Tone, Reeves or Dr. Z, but since this is a combo I don't have to worry about also buying a special cab, which pushes the cost of those amps into the $3000+ range. A tech here told me, straight up, he thought it was a bad purchase. Joke's on him because the amp is way better sounding than my Fender - I just have to crank it like a mfer.

Any recommendations for caps? I saw hificollective.co.uk. Any recommendations for a way to clean the gunk off the circuit board/components?

I'm thinking I could replace the side-mounted caps. The soldering looks extremely basic. To feel comfortable, I'd have to have an exact match, though. A lot of the caps only have two terminals. I don't even know what the difference between the two/three terminal caps is.

Thank you!

[mhuss]

PCBbias.JPG (208.65 KiB) Viewed 3866 times

Note that it's pretty easy to get a blue marker and color the solder joints.

There is one small electrolytic cap on the power board (see attached) for the Bias supply. A lot of inexperienced techs will put these in backwards when replacing them, because connecting the '+' terminal to ground seems wrong (in the U.S. at least ), Pop! Clean up and re-replace using the correct orientation.

The fluffy looking yellow stuff on the switch terminal in the corrosion picture looks a _lot_ like residue from an exploded cap.

I'd try alcohol wipes for clean up, but you'll probably need something stronger (a rust removal product) for the corrosion in the corner. That looks like Coke or something else acidic was spilled there, but I can't imagine how it got inside, much less into just that corner. I'd also loosen up the green and yellow ground connection and make sure that is cleaned up and making good contact with the chassis.

[OldSchoolDave]

I recently bought a Hiwatt Custom 50 SA112 (Serial: 14593) from Guitar Center (got a deal) and I'm pretty sure it needs the caps replaced among other repairs.

My SA112 is a dozen serial numbers "older" than yours. Going out on a limb here....any chance this amp went through a flood? I've not seen that type and extent of crud inside a HIWATT chassis.

To answer one of your questions; the caps with 3 terminals have two sections. One of the terminals is a shared negative, the others are (separate) positives. You might want to let someone else replace them for you. It's definitely an amp worth restoring!

Dave

P.S. I found the preamp on mine to be a bit hot for my tastes and, in addition to running an ECC81 in the PI socket, use a 5751 in V1. YMMV.

[jinglejangle]

I don't think I get emails when I receive replies on this forum - missed your response!

Thank you for the cap information. Really helpful.

I'm not sure what happened to the amp. I bought it from Guitar Center and they didn't really have any info on it. It looks like maybe someone spilled some soda/beer into the chassis?

Thanks for the tube recommendations. I currently have Tung Sol ECC81's. The amp is very piano-like and sweet at low volumes. I haven't been able to really turn it up and determine if a tube switch be would a good idea.

Currently I'm having hum issues after a repair. Argh. viewtopic.php?f=2&t=2211&p=16692#p16692

When switching the amp from standby to "on", is there a split second zzz before the amp is on? Also, I feel like my amp should be louder, considering the fact that everyone mentions how incredibly loud Hiwatt amps are. I can turn the Master up to 10 o'clock and the Bright volume to 10 o'clock and the amp really isn't that loud (a higher than bedroom levels). How quickly does your amp get blisteringly loud?

Thanks!
Garrett

[OldSchoolDave]

I can turn the Master up to 10 o'clock and the Bright volume to 10 o'clock and the amp really isn't that loud (a higher than bedroom levels). How quickly does your amp get blisteringly loud?

Something's not right there...

I've never *had* to run my Master Volume over Noon (with Norm and Bright at 2:00) and in typical gig situations, it's closer to 10:00.

Was this posted before or after you had the amp in for service?

Dave