Hum in an amplifier

Subject: Ho Hum
From: Bert
Date: 14 Oct 01 - 11:50 PM

I picked up this antique (maybe late fifties) Fender amp at a yard sale. It's a 100 watt transister job. Evrything seems to work but there's a lot of mains hum. Anyone got a cure?

Subject: RE: Ho Hum
From: Rory B
Date: 14 Oct 01 - 11:51 PM

Hehehe sing louder.

Subject: RE: Ho Hum
From: 53
Date: 14 Oct 01 - 11:54 PM

old fender amps are great, the hum is probaly coming from the tubes, replace them and that should help.

Subject: RE: Ho Hum
From: wysiwyg
Date: 14 Oct 01 - 11:55 PM

Shoot air and contacts-cleaner in the jack-plug-holes-- see music shop for stuff.

~S~

Subject: RE: Ho Hum
From: katlaughing
Date: 14 Oct 01 - 11:57 PM

Bert, Rog says the filter capacitors have gone bad and are very easily replaced. Any electronics parts store should have them. He says you do have to have some skill and knowledge, be able to solder, identify the components, etc., but I'll bet you have no problem with that, eh? *bg*

He also says they should be replaced about every ten years. Sounds like you scored! My dad had an even older one I wish we still had. We kids had so much fun singing with it and pretending we were on stage.

kat

Subject: RE: Ho Hum
From: 53
Date: 15 Oct 01 - 12:00 AM

i still say it's probably the tubes.

Subject: RE: Ho Hum
From: katlaughing
Date: 15 Oct 01 - 12:00 AM

Rog also says he's assuming that it is humming without anything plugged into it. If you have something plugged in, like a guitar, and it hums, it could be your cable instead.

Subject: RE: Ho Hum
From: Bert
Date: 15 Oct 01 - 12:01 AM

HeHe RoryB, I was thinking of just leaving it and letting it disguise my voice a bit.

53, It's a transister amp, must have been one of the first, it's got a built in rhythm generator with a dozen or so ballroom dancing styles and one labelled "Teen Beat". So it's got to come from the real early days of Rock and Roll.

I'll try that WYSI. I've tried reversing the mains polarity but that didn't help. Surprisingly the pots are still fairly clean.

Subject: RE: Ho Hum
From: Bert
Date: 15 Oct 01 - 12:02 AM

Good point kat, I'll do that.

Subject: RE: Ho Hum
From: katlaughing
Date: 15 Oct 01 - 12:26 AM

He also adds there are only about 3 of them in there and he'll be happy to help you out, if need be. Let me know and we'll give ya a holler sometime this week.

ta,

kat

Subject: RE: Ho Hum
From: Little Hawk
Date: 15 Oct 01 - 12:44 AM

There is one other possibility, Bert...it may not know the words. Specially to your original songs. Try setting up a music stand with the lyric sheet where the amp can get a good look at it, and see if that does the trick. :-)

- LH

Subject: RE: Ho Hum
From: GUEST,Dale
Date: 15 Oct 01 - 01:13 AM

Hmmmm. And here I thought this was going to be a request for the lyrics to Ho Hum and I was about to go looking for them! "Goodbye to Winter, I'll see you next year, Hello to Springtime, Gee, I'm Glad You're Here . . ."

Subject: RE: Ho Hum
From: Rick Fielding
Date: 15 Oct 01 - 02:17 AM

Damn Bert! I thought this was gonna be about a Vietnamese leader forgetting the words to a song.

Rick

Subject: RE: Ho Hum
From: mooman
Date: 15 Oct 01 - 04:10 AM

Sounds a little more like an earthing or cable problem to me. Does it hum without anything plugged in or only when you have an instrument plugged in? If the first suggest check the earth lead first and, if the latter, then try a different, better shielded cable or check the shielding on any internal components in your instrument. If none of that works then the above explanations are the likely cause.

Best regards,

mooman

Subject: RE: Ho Hum
From: catspaw49
Date: 15 Oct 01 - 09:09 AM

Earthing problem? Yes, that could be it. So Bert, go dig a hole in your garden and bury it.

I always loved the Euro terms instead of the US. Positive earth, negative earth......The first is a hill and the second a hole? Seriously, sometimes the Euro stuff is much more descriptive. Spring dampener is far more accurate than shock absorber.

Anyway, nice find on the amp Bert.

Spaw

Subject: RE: Ho Hum
From: Bert
Date: 15 Oct 01 - 10:23 AM

kat, does Roger mean the smoothing capacitors in the power supply, or should I be looking in the tone control area?

LH, fortunately I had just swallowed a mouthful of coffee, or I'd have had to take my keyboard apart again. Perhaps I should try it on some Everly Brothers. "All I have to do is dwe-e-e-e-e-eem".

Spaw, earth and ground are kinda synonymous in England. And I know you wanted to say 'go dig a hole in the ground' but you had to change it to garden to get your point across.

Subject: RE: Ho Hum
From: katlaughing
Date: 15 Oct 01 - 11:11 AM

Yes, Bert, he says they are the smoothing capacitors. He says they are the largest thing in there, anywhere from 2" in diameter to 4" tall. They will be in a large aluminum can or covered in plastic and should have something to the effect of "several thousand mfd" written on them, at 50 or 100 vc. There are usually two and sometimes they are packaged together in one unit.

He also said if they didn't use a output transformer, there could be another one which separates the amp from the speaker, so you have to be sure not to get that one.

Again, he says they are fairly easy to replace, you just have to be able to solder and joila!

He'll be home this evening around 530p our time, 730p your time, if you want him to give you a call, just let me know, okay?

kat

Subject: RE: Ho Hum
From: Bert
Date: 15 Oct 01 - 11:20 AM

Great kat, I know just what they are, just didn't know that they needed changing regularly. I'll get around to changing them as soon as I can find replacements, which may take a day or two. Tell Roger "thanks a million". I'll let you know the results when i've done.

Subject: RE: Ho Hum
From: katlaughing
Date: 15 Oct 01 - 11:23 AM

Super, Bert, thanks.

Subject: RE: Ho Hum
From: GUEST,Roger the skiffler
Date: 15 Oct 01 - 11:24 AM

"Ho' Hum": a noise made by a working girl while waiting for ther client to finish up and get off. (Roger's Thesaurus)
RtS

Subject: RE: Ho Hum
From: Bert
Date: 15 Oct 01 - 08:09 PM

OK, now I know what to do, where do I buy these monster capacitors "2000 microfarad, 30 Volts"? Our local Radio Shack only has piddly little electrolytic ones.

Subject: RE: Ho Hum
From: Greg F.
Date: 15 Oct 01 - 08:22 PM

Try Mouser Electronics:
http://www.mouser.com
Reasonable prices, no minimum order, free catalog, nice folks.

Best, Greg

Subject: RE: Ho Hum
From: Greg F.
Date: 15 Oct 01 - 08:30 PM

Rats! screwed up the clicky! Good thing its a short address. You may have to go with 2200 microfarad (standard value) but they should work fine.

Greg

Subject: RE: Ho Hum
From: SINSULL
Date: 15 Oct 01 - 08:34 PM

Don't touch the Flex Capacitators. You're likely to end up in 1951 and have to relive the folk scare.

Subject: RE: Ho Hum
From: McGrath of Harlow
Date: 15 Oct 01 - 08:39 PM

Spring dampeners? That sounds nice, if a bit wet. But I've never heard anyone call them anything other than shock absorbers.

Subject: RE: Ho Hum
From: Murray MacLeod
Date: 15 Oct 01 - 09:34 PM

Spring dampeners must be a pre-war term, Spaw probably heard it when he was over here servicing the vehicles for D-Day :-).

But, on the original electrical theme, I have been wiring up my new workshop, (with the help of an electrician to do the dangerous bits) and was amazed to discover that, apparently, the USA has never heard of ring circuits, which have been mandatory in the UK since just after the WW11.

Everything is a "home run" back to the circuit board. Can somebody with more electrical expertise than I explain why this should be so? Due to the voltage difference?

Murray

Subject: RE: Ho Hum
From: catspaw49
Date: 15 Oct 01 - 11:31 PM

I was just one of those rarities here in the states.........a mechanic who would actually repair British cars. And worse, I actually drove some along with riding Beezers and Triumphs. At least as late as 1975, repair manuals almost always referred to the damn things as spring dampeners.

Not that anyone over there actually knew how to build a decent one............Thank gawd for Koni! I figure about half of the engineering guys who were so bad that they couldn't even build a telescopic shock eventually went to work for Girling because their vast experience in hydraulic leaks made them a perfect choice for Girling brakes. The other half went over to Lucas where they could forget worrying over leaky o-rings and get down to the serious business of burning Jaguars to the ground.

Spaw

Subject: RE: Ho Hum
From: katlaughing
Date: 16 Oct 01 - 12:31 AM

Bert, there should be some kind of electronics parts store there; we've even got one here. Mouser is good, but it's a lot better if you can take them in and make sure of getting the right ones.

Rog also just mentioned that they are polarised, so there is only one correct way that they go in.

Over here a spring can also mean a rill, so I am wondering how in the heck does one dampen water?**BG**

kat

Subject: RE: Ho Hum
From: catspaw49
Date: 16 Oct 01 - 12:49 AM

Kat, I think our friends across the pond have a solution for you. Again, the good folks at Lucas made wiper motors so weak that they'd barely move the wiper arms and were guaranteed to fail under adverse conditions.....such as rain. The arms had wiper blades that even when new (and assuming the motor worked for a minute or so) didn't remove the rain but rather smeared it around to the point it actually looked wetter and worse than before you toggled the switch! This is why a lot of British sports cars for many years had no windshields but instead a tiny windscreen that acted as a deflector to funnel the water back into your face in two streams as opposed to droplets.

Spaw

Subject: RE: Ho Hum
From: rangeroger
Date: 16 Oct 01 - 12:54 AM

Murray, I'm an electrician. Well almost. I just started my fourth year of apprenticeship, and I haven't heard of "ring circuits".

A home run on a circuit is the wire run between the first device or junction box in the circuit and the panel board.

rr

Subject: RE: Ho Hum
From: Bert
Date: 16 Oct 01 - 12:57 AM

kat, Radio Shack have some small electrolytics that are 2200 microfarad and 35 volt. Would they do? They look way too small, but times have changed since this amp was built.

Hey Spaw, talking of hydraulic leaks did you ever get to work on the power steering of a '75 Volvo 242? Where the stupid effing designer made the o-rings the same size as the rack. To reassemble it you needed a special tool to shroud the rack so that it didn't tear up your newly installed o-rings. I didn't have such a tool so I took the car along to the Volvo Mechanic to get the job done properly. He didn't have the tool either so he wrapped the rack with electrical tape. Of course that didn't work, and the damned thing just kept leaking.

Give me American auto engineering any day.

Subject: RE: Ho Hum
From: katlaughing
Date: 16 Oct 01 - 01:07 AM

Bert, Rog says those should work.

Rog says on a ring circuit the fuses are actually in the outlets? He can't remember, but has read about them in one of his reference. We do fuse panels here.

Oh, Spaw, now I am getting lonesome for my little Cortina! Loved that ground to earth notice under the bonnet! And, lifting the carpet, taking off the trannie plate, to use a screw driver to pop it outta reverse!

Subject: RE: Ho Hum
From: catspaw49
Date: 16 Oct 01 - 01:16 AM

Actually Bert, that was a common design for many years on a lot of racks. The tool you needed was very similar to a piston ring compressor and did a good job. Without it, the job was virtually impossible. You also needed a small cylinder hone to clean the housing properly or the o-rings still wouldn't seat properly when replaced.

American engineering? Well, I can give you more than a few problems there too...................

Spaw

Subject: RE: Ho Hum
From: Bert
Date: 16 Oct 01 - 01:48 AM

kat, great I'll try a couple of those.
A ring main was nothing special, just that the end of the line was connected back to the beginning. They have a fuse at the outlet, in the plug, and a fuse or circuit breaker at the box. Don't know what the advantages of the ring main are though, that's just how they did it.

Ye Gods Spaw, you mean that there was more that ONE designer who was that stupid. If I had pulled trick like that as an apprentice I'd have got my arse kicked. You make the O-rings a LARGER diameter and everything works fine, sheesh and they actually PAID people to think up that crap.

Give me my old Ford truck anytime. half an hour to change the water pump and about two hours for the timing chain. The only design fault that I found was that the fuel filter was too small, but that was easily solved by buying a bigger one at Chequer. Pity the old thing just wore out. It was old when I got it and I drove it for years on gravel roads up in the mountains.

Subject: RE: Ho Hum
From: John J
Date: 16 Oct 01 - 12:45 PM

The problem is almost certainly either an earthing problem or a smoothing capacitor problem.

Electrolytic capacitors 'dry out' in old age / lots of use. To recognise the likely offending components look for large cylindrical components. The markings are likely to be something like 4700uf 50v. This describes the capacitance (value) and the maximum working voltage. As this is a 100w amplifier and fairly old to boot, it's not likely the supply voltage was particularly high (perhaps 50v maximum). It's vital that the replacements are at least the same voltage, and ideally the capacitance should be the same or greater. As somebody else mentioned earlier, these components are polarity sensitive....connecting the wrong way round will result in a big bang! Electrolytic capacitors, particularly large smoothing capacitors should really be changed every 10 years or so.

Regarding the possibility of an earth problem: the suggestion of a squirt of switch / contact cleaner down the jack sockets is a very good one, although if the sockets are very corroded you could replace them easily and cheaply. What is probably happening is that one contact (the 'signal' contact) is ok, the earth contact is probably poor. The effect of this is for the amplifier to have an aerial connected to it's input. This aerial picks up anything that's flying around (eg mains hum) and then amplifies it. Ever tried touching the tit on a jack plug connected to an amplifier? It's just the same.

If you're stuck, email me at [e-mail]

Cheers,

John

Subject: RE: Ho Hum
From: catspaw49
Date: 16 Oct 01 - 12:50 PM

I can't get into touching the tit on a jack plug. Now if you wanna' talk jill plug, that's another matter.

Spaw

Subject: RE: Ho Hum
From: Murray MacLeod
Date: 16 Oct 01 - 06:19 PM

rangeroger, you might like to click here for a brief insight into British ring circuits.

There must presumably have been perceived advantages to the ring circuit (aka ring main) otherwise Britain would not have made the change-over from the old 15 amp system which was esentially the same as the American method of multiple "home runs".

Murray

Subject: RE: Ho Hum
From: Little Hawk
Date: 16 Oct 01 - 06:53 PM

Jaguars actually burn quite nicely without any help at all, but the frame on the old sedans is very durable, built like a Churchill tank to withstand a Bangalore torpedo, so even if the rest burns you've still got the basis for a great piece of modern art or a street barricade in time of national insurrection.

We have a garage in Orillia that specializes in repairing Jaguars, and their claim to fame is that they can take any car that's running poorly (like a Jaguar) and reduce it to a condition where it probably won't run at all! They get very little business, but somehow keep lingering on year after year. Every now and then you see a Jaguar that actually works in town, so that means there are one or two they didn't fix yet, I assume.

I once had a Honda Civic "fixed" by them...twice...in 2 weeks. It never ran right after that, so I sold it to a friend for enough money to pay for the repair bills. He took the carburetor apart and cleaned it (the garage never thought of doing that), and presto! The Civic was running right again. This remains a sore point with me. I loved that car.

Give me Japanese auto engineering any day. American is good too, but nothing runs like a rice burner! :-)

- LH

Subject: RE: Ho Hum
From: katlaughing
Date: 16 Oct 01 - 07:22 PM

Yep, I am on my third Subaru, just about to turn over 200,000, as did the previous ones; actually the first one went to about 280,000!

Subject: RE: Ho Hum
From: catspaw49
Date: 16 Oct 01 - 09:32 PM

Subaru.......A great example of the Japanese learning that Americans treat cars differently and we are a bit different then they are. The early Japanese imports here had a lot of problems ..... rust, low power, not built for larger people, etc. The Japanese took what they learned and ran with it to produce a superior product.

The early Subaru sedans had the rear seat cushion mounted directly on top of the fuel tank. Bigger people, rough back roads, and road salt, added up to seats poking holes in the tank and the occasional disaster that accompanied the problem. Like other things though, they worked it out and they became better cars. Like Gallagher once asked, "Ain't it kinda' weird that the Official Car of the United States Ski Team is a Subaru?"

Spaw

Subject: RE: Ho Hum
From: 53
Date: 16 Oct 01 - 09:35 PM

moved a long way from the amp.

Subject: RE: Ho Hum
From: catspaw49
Date: 16 Oct 01 - 09:45 PM

Right now we're just waiting for Bert to try a couple of the fixes and report back so.................

Hey Bert....Did the pickup have one of the 300 CID sixes? That was a really great engine, torquey as hell and ran when it should have been worn out. Sounded friggin' awful even when it was new, kinda' like a tractor (or an Aston-Martin), but the thing really was a workhorse.

Spaw

Subject: RE: Ho Hum
From: katlaughing
Date: 16 Oct 01 - 10:14 PM

Spaw, we used to have an old 1953 (I think) Studebaker pickup. The three on the tree used to fall through to the ground, so my ex would stop, crawl under, push it back up and we'd go on. One time, we were driving down the interstate at night, had to get home. The alternator went out or was it a generator? Anyway, he made me crawl in the back and hold a flashlight pointing behind us, so we wouldn't get rearended! I gripe about kids today being handed such nice cars, but I would be appalled if any of my kids drove some of the things I did!

Subject: RE: Ho Hum
From: Bert
Date: 16 Oct 01 - 10:27 PM

It'll probably be next week before I get the chance to take the amp apart, so don't hold your breath.

Nah Spaw it was a V8, I don't even remember the size, smallish I think. But you're right about it running when it should have been worn out. The compression was low when I bought it but it was priced right at $900. I figured I'd have to rework the engine after a year or so. But it was still going strong after eight or nine years of mostly gravel roads. I finally sold it for $200 so it cost me less than $100 a year. The biggest repair job was a new half shaft which cost around $100 including labor.

Subject: RE: Ho Hum
From: catspaw49
Date: 16 Oct 01 - 11:28 PM

Ya' know kat, we'd get killed for it, but we need a thread on cars we've owned. Bert's pickup, your Stude truck (generator)...........Studebaker....great cars and sadly gone. However..................

I had a friend who was in his fifties (I in my 20's) who collected Studebakers. He had a beautiful and rare Speedster model and an equally beautiful '62 Hawk. He was rebuilding another Hawk and had several parts cars, one in driveable condition. On several occasions he'd sold it to one of us to drive while we worked on whatever we had. My turn came when I was rebuilding the 455 in my '70 Goat. Warren sold me the Hawk for $100 and as always expected to buy it back when I was through.

This old Hawk had a lot of good parts and a lot of bad ones too. The engine was in decent shape and the old girl ran like a bat outta' hell but the steering linkage was shot.....not a good piece, tie rod or idler or pitman to be found and at 110 the thing set up a shimmy that would damn near yank the wheel out of your hands. I look back and wonder what the hell we were doing driving the thing that fast to begin with, but the young know no mortality. It was also rusting out here and there, to say the very least.

It's February, the snow is blowing a dust around on a very cold wind, 3:00 in the morning and Howie and I are still working in the shop on the goat. For reasons known only to god and the very young, we decided to take a run out to the truck stop for breakfast and then come back as the shop opened at 6 AM. It's also unclear to me why we took the Stude instead of Howard's winter beater which was a very decent Ford pickup. We took off and about 15 miles out the freeway the oil pressure dropped a lot and we pulled over and checked the oil, but it looked like the oil pump was fragging.........Can't fix it, so might as well eat. Another ten miles and the rust caught up with a headlight which fell out so again we pulled over and with some judicious applications of electrical tape (we had no duct tape in the car) we were off again.

Had a nice, big, greasy, breakfast and started home, only to find that there was this funny clunk in the differential when you started out and as we turned, you could hear the diff spinning and you lost go power....spider gears were gone. I guess the folks back in South Bend had programmed this old girl to self-destruct on this day some 15 years after it left the factory. Luckily, I only had a few hours to go on the GTO so I really didn't care.

Then a funny thing happened. This kid walked into the shop a couple of days later and asked about the Hawk. He was 16 and dying for a car and just loved the way it looked......I mean he was all excited about the thing. Before I tell him I can't sell it as Warren wants it back, he whips $300. out of his pocket and says it's all he has and will I take it? Well.................Warren was really pissed and didn't speak to me again for years and later, when I saw "Christine" I recognized that same look the kid had when Arnie viewed the Plymouth. I felt a bit bad about the whole thing, but money talks, bullshit walks....... and I needed the bucks.

I saw the kid about a month later as he turned the corner in front of the shop. Three other kids hopped out as he turned to get the Stude around the slow turn, the spider gears must have been completely gone at that point. I was out front getting a car to pull in and he gave me a big wave with a smile. Happiness is a fine thing ain't it?

Spaw

Subject: RE: Ho Hum
From: rangeroger
Date: 17 Oct 01 - 12:16 AM

Murray,thanks for the link. I printed it out and will show to my instructors.I can see no reason for it either. I would love to see how the connections are made in the panel (consumer unit).

Bert, I had an old Dodge pickup that was almost indestructable.225 slant six. One time I drove it for 3 days with a broken crankshaft.Had a vibration in the drivetrain that went away when I put the clutch in.On my days off I droppedthe tranny to check the clutch and found that the flywheel flopped around.Dropped the pan and saw that the crank was broken between the rear main and the #6 rod journal.

I was able to drop the crank out the bottom without pulling the engine. Had it running 3 days and $200 later.

Try that with a Jag.

And to bring he subject back to music,I'll break out Greg Brown's CD and try to transcribe the lyrics to Slant Six Mind.

rr

Subject: RE: Ho Hum
From: katlaughing
Date: 17 Oct 01 - 12:58 AM

How about John McCutcheon's "The Red Corvette' aka A TRUE STORY?

Man-o-man, Spaw, what I'd give to have a Hawk! Loved those things! And, yer right about needing a BS old cars thread!

Subject: RE: Ho Hum
From: Little Hawk
Date: 17 Oct 01 - 01:39 AM

Funny, Spaw, I don't remember that incident at all...? Are you sure it was me? Maybe I have a doppelganger out there somewhere?

I've got a Subaru now, and it's a great car.

- LH

Subject: RE: Ho Hum
From: kendall
Date: 17 Oct 01 - 06:23 AM

You may throw rocks at many English cars, but, until you have driven a Rolls Royce, you must not condemn all of them. I have driven just about everything with wheels, and, the most impressive car I ever drove was a new Rolls Royce. That was in 1960, and, I can still say that.

One of my earliest trips to Canada was on Air Canada. I did not like to fly, and, had just read "AIRPORT". Antsy as frog on the freeway with a busted hopper, but, I looked out the window at the engines. When I saw the Rolls Royce logo, I felt a little better.

Subject: RE: Ho Hum
From: catspaw49
Date: 17 Oct 01 - 07:12 AM

I ain't condemning the damn things Kendall....Hell, I loved them! For all of the quirks, they had something wonderfully magic in their little mechanical souls. But don't let yourself believe that Rolls was/is the be all/end all of the automotive world either. And on a strictly value for pound basis, the old Humber Saloons were hard to beat.

Spaw