Dull Hum Amp Sound Question

Dan

Good point. I assumed it was a tube amp because it is 20 years old. Bad assumption. Maybe ABLE1 can post the manufacturer and model.

Dan

Such things keep life interesting. Now that this thread's drifted to dark humor, allow me to embellish my first followup, which talked about the direct connection of a twisted pair to an audio jack of a phone system. Neither an amp nor a passive balun was installed. Phone guys usually excel at pulling twisted pair cable. Except when they leave one end of a cable coiled up and unterminated in the plenum, for the next guy (me) to discover. :)

Thank you, 73,

Would that cause the symptoms reported, though?

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The road to hell is paved with false assumptions. In fact "assume nothing" was top of the list of tips on the troubleshooting group sci.electronics.repair.

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Dearest Phil,

I had typed a very nice and pleasant detailed response to you message. Sadly, I clicked on the wrong button and it was lost..... to a deep dark hole and will never return. So much for being nice.

I was going to try and retype it all again but, I then figured whats the point. You would only find a way to have the last word anyhow.

And 'Yes', I did mistakenly type to the wrong newsgroup. Whoops!! My bad.

I would like to thank all those that have responded to my quest with some insight on the problem. I will move forward by getting the Mfg. and Model number of the Amp. Hopefully I can then find the manual and maybe the schematic. Might even be lucky enough to get the specs on the Caps that would be installed.

BTW the Amp is mounted on a wall in a small closet. When it was originally installed it would have been easy to access. Now, there is a Network rack, router, PC, etc. in the way with makes it extra challenging. Evolution is not your friend.

To all those that are reading and not posting my hope is that you will benefit from this thread as well. Over the years I have gleaned added bits of information from various newsgroups just in reading the postings. It has all been a silent bonus. Enjoy the benifits!!

Again thanks to all for the assist and insight.

Have a good week.

Les

Just because you are an expert having great knowledge in the audio field, doesn't mean you need to be an expert with great knowledge to replace defective power supply caps in an amplifier. I did that my first job out of a gas station fuel pumper at 17. Starting with the Dynaco 120. Now as to whether that fixes the problem is still in question but with your HELP, he might be able to figure out if the odds are most in favor of bad caps. What do you say, do you want to help or just bitch. Mikek

PS, if you decide to deride and berate me, try to use something new that will at least entertain myself and fellow posters. Thanks

Could do. The main rails, filtered by the BFCs, may happily have 0.5V or more ripple at idle but the input stages demand a much smoother supply and are fed by RC decoupled quiet rails. Those BFCs tend to last much longer in my experience than the little cheapies!

piglet

You won't be able to - you stupid, ASD f***ed nut case.

..... Phil

That wasn't just a false assumption. It was also a spectacularly stupid ass umption.

Twenty years ago is 1999. In 1989, tube-based amplifiers were already antiq ues - some audiphools actually bought tube-based audio-amplifiers back then , because they liked the distorted sound they produced, but those amplifier s were expensive luxuries offered to buyers with quite a lot more money tha n sense.

People setting up public address systems weren't that foolish - valves need ed replacing every few years and transistors didn't.

Where did I put the ashes and sack clothe?

Dan

OK, as a follow up on this Amp challenge the following is new information.

At this point I think it is safe to say that the Amp and/or Caps in the Amp are defective. It matters not, since a new replacement is the obvious next course of action. On either end on the heatsink there are a couple of transistors 2N5881. The Caps are not visible, so it would need to be disassembled. I will do so after I remove and before I place in the nearest dumpster at the recycle center.

That is unless someone wants to pay for shipping and you can play with it. Otherwise it had a good life.

Side Note: It is a shame that 'some' have found it necessary to get nasty in the postings. All I can say is what was the point?? I know for 'some' anything said about the negative action will fall on blind eyes. It is my opinion that the Usenet is or was designed to give the users a way to help others. It is very sad when all goes into the toilet.

Thanks to all of those that assisted with good help and insight. All is appreciated.

I will now go back to lurking and picking up little tidbits of info.

Have a good rest of your week.

Les

Uses transformer drive as well as output for 70V lines. Single supply rail with one, 10,00uF 50V electro. See manual with schems:

FYI: There is a bad drawing error in the power stage for the 1110 model concerning the output transformer primary connections.

In any case, an genuine antique in the world of line voltage PA amps and long overdue for retirement.

Rest of Mr ABLE's meandering drivel snipped.

.... Phil

Just my two cents. Sounds like you're in the alarm system business and thi s is a customer with a business that has a four story building that uses a paging system. IMO, since this system isn't your forte, why get yourself involved in screwing around with it? Probably better they get the right te ch and if they are a business, they should be able to afford one. I'd be conc erned that something will go wrong and I'd get blamed, lose a customer, etc. Like Clint Eastwood said, a man has to know his limits.

OK Assuming I'm wrong, I haven't checked,

does that mean you are know going to pitch in and help?

Tired old Same O same O. Really now, I ask for better*, step up your game Phil!

• even though you snipped it.

Nice job Phil, helping is good. Mikek

PS, please correct the typo, others don't know as much as you, and might not know how to interpret that value.

Hi Trader,

Your 2 cents are almost correct.

However, this is a Non-Profit and I am on the verge of making a new Amp a donation.

I have been doing a wide variety of work for them for over

The donation will be well received.

Very good customer and they like me!!!

Les

I am pretty frugal and at one time would have taken it and replaced the c ap. Since it is 28 years old , the big electrolytic cap is almost sure to be bad or at least bad soon. But I have no use for it. You might list it an Ebay before putting it in a dumpster. Back in the sixties the mean ti me to failure on hi-rel transistors was estimated at 1500 years. So most o f it would still be good. I once replaced about a dozen caps in an Hi-Fi receiver.

Dan

1500 years equates to one unprovoked failure in 1500 units, per year, within the expected life of the device and assuming normal use conditions.

A 28 year old, wall mounted PA amp that has seen 24/7 operation will be suf fering severe deterioration in almost every component as well as the PCB it self. Even soldered connections are no longer trustworthy and push on types only functional by sheer luck while on borrowed time.

FYI:

TO3 BJT devices using Aluminium packages were rated at 5000 thermal cycles before failure. This is why Motorola and most others changed to steel paks sometime in the 1980s.

A paging amp in constant use would be a sitting duck for this sort of failu re.

.... Phil