136A in L300 problem

[Donald]

L300s driven by Carver M-500t. Worked fine last night. This morning I powered on the amp and walked away. When the speaker delay relay closed I got a very loud, continous sound. I hit the off switch as soon as I could. Disconnected the speaker and powered on the amp. Power meter needles pegged. Both channels. Disconnected input and amp behaved normally. Connected cable to one input and touched the center connector of the other end. Meter needle indicated an input. Switch to other channel and it behaved the same. Connected the original input cable and power needles indicated no input. Upped the volume on the pre-amp and needles behaved fine. Connected L300s again and all seemed OK. Except right speaker had no bass. Checked 136A and cone is pulled in tight. Removed driver and checked resistance. Still have 6.5 ohms resistance.

Any suggestions on how to free cone? I tried gentle pressure on the backside of the cone. No go.

Should I send to OC Speakers?

[John]

Sounds like things heated up in the coil and bubbled the insulation on the coil resulting in a draging coil.

I am very sorry and I feel your pain.:(

Recone is the only real fix.:blah:

This is the risk we take with vintage amps more so than newer amps.

[Donald]

How fast would the coil heat up? The noise did not last more than 15 seconds.

Started watching a movie and it happened again. Driving my L222 Discos. Removed M-500t and inserted a Carver M-0.5t. Finished movie with no problem. The M-500t needs service. Suggestions?

Pics show a view inside the rear vent of the 136A. There appears to be an aluminum spacer that is not centered. Not sure how this could have happened during the recent problem.

[John]

That thing you call a spacer is the top plate. I do not believe that is your problem. As far as how long to cook a coil, well it could happen in 4-5 seconds if there is enought juice sent to the coil. Sounds like the amp is flirting with D.C. current being applied to your coil.

I have personaly viewed a Flame Linear go DC on a pair of 4311's and within 5 seconds both L.F. 12's were frozen and dead. The 4311's were being audioned by me when the tragic event occured, needless to say the deal did not go thru but I felt a loss just the same.:(

[Donald]

I found a 136A on eBay with a BIN. So I did. Then I remembered I had 2 136A in my stash. But they need new surrounds. :(

I now have 3 136As that need work and a few LE14A that need work. Time for a trek to OC Speakers!

[Doc Mark]

Greeting, Donald,

Sorry to hear about your woofer problems. Those sorts of problems can never be fun, that's for sure.

I have a good friend who had his Carver amp go South on him in an odd manner, too. We had made him a subwoofer, which mounted inside an "alcove" in his wall, which contained a pair of 2235H's. His main speakers were a set of Control 5's, if memory serves, and that system sounded very good and quite powerful and dynamic!! He was driving it with a pair of Carver offerings, one a receiver, I think, and the other an amp, bi-amped. One day, his Carver amp discharged some kind of HUGE power surge through his subwoofers when he turned off the amp!! I was standing in front of his subwoofer when it did this, and the energy coming of the box actually moved my blue jeans pants legs, like wind!!! Scared us both!!

He immediately took his Carver amp, which was basically brand new, in for service, but they told him it was fine, with no problems, at all. So he put it back into service, and it did the same thing again, immedicately upon turning it off. Back to service it went, with the same results: they could find nothing wrong with it! In disgust, my friend sold off both pieces of Carver gear, not trusting either one anymore, and bought something else, which worked like a champ. He's still using that system today, with not a peep out of his current amps, whatever they are. To this day, he has nothing good to say about Carver amplifiers, however...... Take care, and God Bless!

Every Good Wish,
Doc

[RKLee]

Donald: I am not sure, but it is not good. "Sounds" to me like your failed amp ripped the voice coil off the VC form. I had power amp failure once, I literally had a flames in my amp on the circuit board. I switched the amp off ASAP, but it was too late. I even with a fused the input even that was not enough to protect my 2 Altec 414 woofers in the left box. It melted the fusible link in the fuse. I had to have both woofers reconed at a princely sum of $35 each woofer(parts & labor) using real Altec cones. The woofers(NIB) originally costed me $70 each in 1975.

BTW: the amp was a kit-built Southwest Technical Products 210 Tigersaurus amp. Hard lesson to learn, no more kit built amps. I still have the other SWTP 210, that I am a bit gun shy to use. My other self-built kit SWTP amps works okay to this day, 25watts/ch, and 60watt/ch.

[John]

I found a 136A on eBay with a BIN. So I did.


I hope you are not talking about the one in CO. that had a aftermarket kit in it???

[Donald]

John,

It appears so. Why?

[subwoof]

Bob carvers old company was phase linear...and was well known for the "flame linear" moniker.

Those carver amplifiers exploit the core magnetization hysteresis in a "loose" wound power transformer to get the light weight "magnetic field" power supply and are not the best choice for critical listening / use.

The power supply caps ( there are quite a few on 3 different HV voltages ) either go dry or burn/shake loose the leads - a total re solder on them is **mandatory**

It only takes a few seconds to toast a 150.00+ coil and this sounds like an intermittent issue that WILL HAPPEN AGAIN...

So yes, have it reconed and put the phase blazes on ebay.

[gsb001]

Carveraudio.com is an excellent forum. Great group of people. I highly recommend this site.

I’m running two Carver M500t’s on JBL’s. I’d love to see what they say. I’ll post the question to them.

Steve

[Donald]

I am aware of the carveraudio.com site. That is who I will contact.

Looks like in-line fuses are needed when using vintage amps. :)

It appears the 077 is also blown. Will the 2404/2405 diaphragm work?

[Donald]

Well, 077 ohm test is OK. Connected to a signal generator and I got sound. My only concern is the front of the mounting flange has a sticky film. Not sure where it came from.

Guess this will go to OC also.