Hello all,

I have a Bogen TPU100B that has 2 leaked Capacitors on the main board. Leaked "goo" over a number of components. UGLY!!!

The result is that it keeps tripping the breaker.

Anyone know of a repair service or a source of a replacement board??

This amp is set up for a 70v system. There are a number of speakers (maybe 12 to 15). The resistance at the connection wires is 2.5 ohms. Before I start tearing the wiring apart to look for a short can anyone tell me if this resistance value is approximately correct??

Thanks in advance for any insight.

Les

At 70V 2.5 ohms you have a nearly 2000 watt load, which is not acceptable for 12-15 speakers nor the TPU100B. Did you check with a DMM in resistance mode or with a proper impedance bridge such as a TOA ZM-104?

You can also check for ground faults by measuring with a DMM between earth and each leg of the speaker wire.

Bogen is still in business so you can contact them for repair or a new part once you verify with the proper tool whether or not you have an overload. https://www.bogen.com/

Tim,

I used a DMM to get the 2.5 ohms. I know it is not the proper device but it all I have. I was in a rush and should have checked each leg to ground. Will do that tomorrow.

I get the feeling that I may have a bigger problem and should start dissecting the speaker wiring.

I was not sure about Bogen doing repairs or not. Customer may just go for a new replacement. Just need to work up the cost numbers.

Thanks,

Les

Then you might as well not have bothered because DC resistance means nothing. You need an impedance meter.

That aside, what makes you think those leaking caps have anything to do with a speaker or line problem?

Is the amp old? Is the ambient where its located hot? Do you know how to simply replace them? You don't need a new amp or board. If it trips the breaker they are power supply filter caps.

-Hal

I get it, I really do. But am limited to what I have (at this time) to work with.

As I see it the caps could have died due to age. Approx 30+ years.
Environment not hot.

It could have be a bad wiring short or speaker txfmr. Again 30++ years.

I could replace the caps, clean up the board and then find that the there are other problems. Wasted time and effort.

Just got green light from customer to install new amp.
Need to check the speaker grid to make sure I don't have a problem that the new amp will not like.

Searching locally to see if to see if another contract has impedance meter I can borrow for a while.

Thanks for the assist.

Les

Without an impedance meter (Sandman used to sell them) you are whistling in the wind. For years I thought I was good enough to service sound systems with nothing more than a VOM and a speaker. 50 years ago, one could get away with that.

When I was running service for a National and most of the work was trying to get miserable and butchered sound systems to work in large stores, I bought an impedance meter. That is one of the BEST investments I have ever made. Not only will the meter tell you where the problem is, it can also tell you if the amplifier can handle the load. It was easy to find all the 8 ohm speakers "glommed" onto the 70 volt lines. What used to take 1/2 a day to sort out and track down because a 15 minute job.

Rcaman

It's not the best meter but it will do the job for a cheap price.

MCM Electronics

LOL I have one of those...it sucks. My old analog U-100? whatever, works a whole lot better.

Carl

Even faster is to disconnect the speaker line from the amp and put 120v on it. Heck, you won't even have to remove them after that.



Probably a good idea but I wouldn't go out of my way right yet if you don't have an impedance meter. How many and what kind of speakers are there anyway?

Connect the new amp and see what it does. Watch the clipping indicator as you increase the level. If it illuminates with little output from the speakers you have a problem. If you get proper volume at a reasonable gain setting everythings probably OK. Walk around and listen to each speaker. If you have one that is a lot louder than the others it's probably one without a transformer.

These amps are pretty well protected and as long as you don't leave them connected to a dead short and crank the level up they will be OK. That old amp died from old age NOT from a speaker problem. There should have been a hum problem long before those caps self destructed so your customer should have known something was up long ago.

-Hal

Ok, I have a TOA ZM-104 on to way to me. Should have by mid week(I hope). Really should have bought one a long time ago but I do minimal audio systems so it never was a bid priority.

Mostly is was a new install so proper planning and install problems did not happen. Rarely was there a problem after the install. I installed this amp on existing speaker grid and all was good 30+ years ago. Now it is a new building owner and the amp needs help.

The impedance meter will be a good thing, no question. It will pay for itself just on this one job so I am happy.

I agree that just throwing in the amp and see what happen is possible. However, I know Murphy all too well. If I am not pro-active Murphy will win. At least getting the meter will absolutely confirm that the speakers are all good. I do know how reverse logic works.

So, I am good to go.

Thanks for all the extra input.

Les

Impedance Meter

This looks like what Sandman used to sell. It looks identical to the one I use. It works really well. I also have an University Sound LWT.

Check Ebay . I have seen these go for as little as $10. The tester is analog and it does take a little time to learn how to interpret the results, but it is a really good tester.

Rcaman

I've used the Goldstar units. They work very well and are extremely accurate. Reasonably priced.

Test it on a bench first. Set out a couple of speakers, hook them up to each other (without an amp) and connect the meter. Check the results compared to what you've connected. Try the different frequency settings, you'll get the hang of it quickly.

Sam

Ok, installed the amp today.

But!! Before I did, I checked the speaker grid with MY (new to me) TAO impedance meter.

I found one speaker wire at 60 watts. The rest of the speaker circuit was a little over 60 watts, total. I pulled the one wire out and tagged bad.

Given the size of the building and the fact that 70% is unoccupied(mostly storage) I decided to let the customer determine if there is a problem at any of their needed locations as opposed to trying to track down one speaker.

Hooked up the amp and tested, all ok.

Soooooo we be good.

Once again no weekend for me...............

Thanks all.

Les

Glad it worked out. Having the right tools can make all the difference.

Sam

I assume you mean TOA ZM-104 meter. That's a great meter. That will pay for itself within a few sound system service calls.

Rcaman

Yes it is a TOA ZM-104.

Not that enthused with the analog movement.

Arrived on site and my hands were full with shipping box of new amp and carrying the meter and the meter slipped out of my grip and hit the floor. When I first hooked it up I noticed that the dial face had shifted forward and the needle was dragging on the face.

Had to a total disassemble straighten the dial face and re-assemble.
Used a new speaker to verify calibration and all was good.

Needless to say feeling stupid, but, not ashamed enough not to post.

I feel that if my telling of my whoops may help someone else to be
extra careful with the analog meters. I would say that even though I was unlucky I was lucky enough.

Later,

Les

When it comes to instrumentation, I make it a point to carry ONLY the testing device and nothing else. Many decades ago, I was on top of an eighty foot tower with a Blonder-Tounge RF meter. At the time, that meter was well over $2,000. Being young and full of myself, I elected to forego the cumbersome strap that was to be slung around my neck to hold the meter. Instead, I thought I could hold the meter in one hand (it weighed about 40 pounds) and adjust the yagi antennas with the other. The meter slipped from my grasp and in a moment of sheer terror, I kicked out my foot off the tower and caught the falling meter with my foot. The meter banged on the tower and I had to contort my body in what was described as a "circus" maneuver to try and retrieve the meter which was dangling, precariously, from my left foot......which was getting a really painful cramp.

Fortunately, I was wearing a body harness which was clamped to the tower. I managed to recover the meter which was no longer functional. I descended to the ground only to find that the batteries had become dislodged and needed repositioned. The crew working with me NEVER let me forget that blunder. Since then, I take very much care with all the test equipment I use.

Rcaman

You could have just used a resistor, more accurate. Value of your choice but I would use several to cover the range.

-Hal