Carver TFM-35x: Smokes and Then Repairs Itself!

[@Giblet535]

I'd tap the left protect relay with a screwdriver, watching the scope. Relay contact shmoo will give off smoke when it's behaving like a randomly variable resistor instead of a switch.

[@rolfts5762]

1) Thanks for video Tony. 2) Maybe it was only some 'fod'-foreignObject that smoked/burned between component-legs, and then/thereby disappeared.

[@1959Berre]

Cold (high resistive) solder joint pulled a lot of current intermittently, which heated it up to the point of soldering itself. That smoke may have been a tiny bit of left behind flux burning off.

[@jamesvw769]

Not likely moron.

[@martinmiller7623]

Love seeing vintage equipment Bob Carver !

[@williamchalmers3132]

BOB CARVER MADE GREAT AMPS. LOVE THE SOUND.

[@dl7majstefan753]

Did you consider a small fly or spider inside causing a temporarily short, which had been barbecued (well done)?

[@mtabernig]

a spider has too much resistance to present a problem. the exoskeleton is basically a non conductor

[@dl7majstefan753]

@@mtabernig Yes, but i just wanted to bring another idea into discussion. Even a spider/fly can carry some humidity and dirt - and the rest is a question of the applied voltage and the impedance of the circuit at the point where this animal walks about…...

[@samuelfellows6923]

😆 - similar to a fly zapper

[@williamsquires3070]

Some suggestions: 1) try tapping on the board, instead of merely pushing on it. 2) try “freeze” spray, or heat from a hot-air gun, and see if you get a sudden change. 3) try running a real audio signal through it, and randomly change the volume up and down. 4) do no’s. 1 through 3 with the top off, and the camera running, in case more smoke comes out! 😃 5) I think you’re going to have to lift out the left-channel board at least, and see if there’s a burn/char mark on the underside. You might even find a crispy critter (a.k.a. dead bug) was what let the smoke out.

[@xraytonyb]

Thank you for the suggestions! I actually did try pressing on the board, but no luck. I also used the freeze spray, both when it was tripping the protect relay and when it was "behaving". The freeze spray was inconclusive, as sometimes the problem seemed to change and sometimes it didn't. I had an older Pioneer amp that did this same thing and it turned out to be a very intermittent transistor. It wasn't a thermal issue so much as it was a faulty lead connection to the actual silicon inside the case of the transistor. This is why you will often see me replace all the small transistors in these older units. Thanks for the suggestions!

[@johnfriedmann2413]

Still a very interesting video... a mystery is always interesting! May have been some debris in the Speaker Safety gizmo. Once it burned off, it was able to operate normally. Maybe?

[@jensk4921]

John great thoughts, I assume you mean the speaker Relay? I feel what you just stated may be what I just experienced.

[@dyotaman]

Great channel! Check the relay vent holes and see if they are clogged. Ozone gas is produced when relays "make" and "break" the connection. This can lead to oxidation of the contacts.

[@JeffCounsil-rp4qv]

I recently had one of these on the bench. The transformer had open windings.. So when it smoked, it stayed dead. ;-)

[@JamesEscobar]

Great video as always! No one noticed the wisp of smoke at around 22:36, right after you say "roughly". 😉

[@TechGorilla1987]

I used to bi-amp stereo with 4 of these. I had more money than brains back then. I absolutely LOVE carver equipment.

[@geirendre]

I would also consider checking the underside of the PCB as you suggest. Both for bad soldering but also to eliminate the possibility that something has fallen under there and got jammed between the PCB and the bottom case. A screw or something that's wedged in between and partly shorts one ore more traces to ground could maybe explain some of the strange behavior you experienced.

[@mrpedrodrodriguezsr7628]

I had a problem similar to this one a long time ago and it was oxidation on one of transistors leads that shorted temporarily and then it opened and everything started working normally as this Carver did . I just cleaned all the transistors leads with a small metal brush and it worked fine . So see if that's your problem . Good Day !

[@OnTheEdgeNow]

I enjoyed the video. It challenges me to think about what is causing the problem.I find the comments very interesting as others contribute their thoughts and ideas.

[@vinnievintage7725]

Tony..., to listen as you vocalize your INTERMITTENT troubleshooting thought process and discuss "OPTIONS" from most likely to least is for me very "educational". When things are cut and dry or go as expected your internal thought process sometimes remains unintentionally hidden! LOL. Great job!

[@jonwright6661]

Similar experience in my case too. Had decent load on the amp, played for 15 seconds. Smoke came out on both sides by Protection relays clicked off and lost sound. Turned power back on and both channels sound great. Found burned resistor that powers relay coil of protection circuit. Protection circuit doesn’t shut down anymore. Amp probably won’t have protection any,ore.3

[@mjmcg]

I have 3 of these amps (TFM-35X) Two running mono up front and one in 2ch mode on the back channels. The two on the front are identical, the one in the back is a different generation as it has two large capacitors mounted horizontally behind the transformer whereas the other two have the upright caps like the one in this video. The one in the back began tripping out during a movie one evening so I took it out of service and benched it. When it's powered on it acts as expected. but after a few minutes warmup time the output relays begin cycling in and out. I started poking around with a wooden probe looking for a bad solder spot as this usually proves fruitful almost immediately when I've tested other components over the years. I had a new set of output relays on hand in the event they were the cause due to age. When I gave a little push on the right channel relay it felt loose on the board. Not flopping around mind you, just had some play to it. When I continued to poke at the relay a heard a sharp "SNICK" come from that area of the board with an accompanying barely visible whisp of smoke that dissipated as quickly as it appeared and left no real odor in it's wake. However, much like you amp... it's working fine now, no relays tripping and both channels seem operational. For the time being it's back in service. The magical, mysterious self healing 35X!

[@hernancoronel]

Could it have been a case of a cold joint autosoldering itself? Highly improbable but a potentially posible explanation.

[@hestheMaster]

I was guessing it was a cold solder joint with a large resistor or diode before you mentioned it. So much amps heated one side of the joint that it remelted the joint ,hence the smoke, and that allowed the juices to flow into the rest of the joint and the circuit went into its normal state. I'm going with that! You'll need to confirm it by looking at the bottom of the board.😑

[@goodun2974]

Another issue to keep in mind when working on Carver amplifiers and receivers. If they have a A & B speaker switching capability, the output relays will be double pole double throw devices and the 2nd pair of speakers gets wired in series with the 1st pair through the additional contacts of the relay. There is an extra pair of contacts in series with the speakers that you aren't even aware of and aren't obvious until they start interrupting the audio signal because of oxidation or pitting on the contacts. They are usually sealed relays, and although it is possible to cut them open and clean them, It is a chore to get the contacts scrupulously clean and properly aligned so that they mate snugly with no resistance, and therefore I recommend just replacing them.

[@randomrepair1680]

The board come out not bad. Undo screws on board and heatsinks and the whole think will tip up and stand on the ends of the heatsinks. Pretty easy to run and test, there is a ground that unscrews with the board so I always would clip it to chassis in this service mode.

[@xraytonyb]

I think that will be my next move on this amp. Thanks for the advice!

[@basspig]

Sometimes a metal oxide resistor will have a layer of dust on it and when the resistor heats up to operating temperature the dust will burn off and give off smoke. And as for your gain disparity between channels some of these TFM amplifiers have an adjustment potentiometer on the driver board which adjusts the gain of the amplifier.

[@mdzacharias]

I've seen intermittent issues with the bridging switch cause a channel to drop. Cleaning that switch helped. Just kinda wiggling the switch while observing the amp output will show it.

[@sonicfuker]

Hey Mark Z, where the hell ya been? Still fixing audio shit?

[@leonardosemienchuk7437]

Gracias por los videos! excelentes todos, me enseñan mucho!! fantastico!!!

[@williamchalmers3132]

I Have replaced the output relays as they are a common problem with the 35x i have and the 2 55x carver amps i have i used equivalent Omron relays. This fixed the intermittent operation.

[@fredjohnson9856]

I have one of these amps from new. The black on the transformer may have been put there to stop turn-on noise. I glued a piece of cardboard onto mine to stop the thump of the cover pulling down when the amp is turned on.

[@mannybarbosa9312]

Did it work cause mine to-45 does the same

[@fredjohnson9856]

@@mannybarbosa9312 Yes it helps

[@ElectronicMechanic50]

I've seen dirty contacts inside the relay smoke and what ever burned off fixed the issue

[@GeorgeGeorge-xj2bc]

Maybe some small signal transistor in the early stages when is cold is malfunctioning and causing instabilities,later after few degrees warmer it fixes.I have seen it in many car amplifiers and also with the opposite effects,when heated a problematic small signal transistor burns the output power transistors.

[@Homer19521]

Looks like some bad solder joints on the little board attached to the back of the amp. Look at the 4 large horizontal pads.

[@xraytonyb]

I actually unplugged the input board from the main amp board and the protect circuit still tripped (until the amp fixed itself). The problem seems to be on the main amp board and is acting like a very intermittent transistor. Thanks for the suggestion!

[@Homer19521]

Yes, but a cold solder joint on the input board could cause one channel to be weaker or intermittent.

[@matambale]

The HAL 9000 recommended re-inserting the original AE-35 unit and waiting for it to fail. Careful on that; it didn't go well for the tech.

[@kjellmartindanielsen8069]

The amp was cold when you started and the left channel was low. It indicates that somthing perhaps had bad contact and when it got hot it went OK.

[@dell177]

That type of problem is a PITA. The only suggestion I can offer is try alternately hitting the signal area with heat and freeze spray to see if you can excite the bad part. I once had a Hafler power amp (60w per channel)that would occasionally flake out on one channel. After a few hot cold cycles it came down to a small signal diode in the bowels if the input circuit intermittently shorting. That diode just had a few ma going through it and not more than 5v across it worst case. I popped in a 1N914 and problem solved, stable under all conditions.

[@johnnygeeful]

SoI have the carver m1.5t and haven't used it in a while. Decided to plug it in, and when I did big puff of smoke I quickly unplugged it. Didn't have speakers or anything just the unit. Opened it and everything looked fine. Next day plugged it in and all good. Played just like nothing happened. Weird!

[@basspig]

Okay at this point I'm thinking there was a bad solder joint maybe related to the relay and the protection circuit and as current flowed through it it aren't made some smoke and soldered itself back together maybe reheated and melted the solder.

[@jonka1]

could it have been conductive debris that was partly shorting on the left channel? If so you would get the smoke if it vaporised and the amp would then be working.

[@mtabernig]

Freeze spray perhaps????? Carbon resistor internally cracked? any resistor lead not touching the element properly? Freeze spray will tell you about all of those problems. also heat is generated with a current flow and not on a signal flow.

[@Internutt2023]

Freeze spray will also expose any cold solder joints on a board that can cause noise or glitchy signal issues like Tony has here. I've used it with success in troubleshooting intermittent issues more than once.

[@Slartibartfas042]

Just some thoughts on the "magic smoke" that you were smelling and that magically seems to have gone back again - what can smoke? Resistors (usually can be seen on discolouring/ changing colour. Electrolytics may vent out and blow some of their ingredients out which would be bad thing for the tracks of the PCB. It could have been one of the coils of that region. The Transistors could be the cause but they won't smoke without then really really quitting their service ;) They would only give some slight hints of the region where the cause can be found by blowing up all components in their neighborhood. ;) So, I would maybe doing quick-check of the electrolytics for spilling and check if there could be seen some burn marks on the PCB/ Resistors/ Coils and then do check with freezing/ heating up if some components would react on temp changes. That's all you could do. Thanks for the video, it's good to see you also get into unclear situations like I feel I would do again and again and .... ;)

[@frankscarano4708]

I was thinking one of two things... The relay itself having bad contacts or not mechanically closing right and acring?, was it driving signal when it smoked? it could have been the relay itself that smoked on the contacts. Other things i have seen with carver is cold solder connections especially on those larger TO-126/220 devices.

[@PeterMilanovski]

This to me looks like a good job for a very sensitive signal tracer! I have seen (I think that it was one of Paul Carlson's videos) where he would bring the probe close to a resistor and you can hear it resisting, literally! Some resistors are really noisier than others and the bad one's (even though they still function) are arching inside and adding distortion and noise to the signal... If a signal tracer isn't handy, an old head from a cassette deck makes a good probe. All you need then is a very high gain input on and amplifier, either the cassette deck or phono inputs should do... Connect a spare speaker and be prepared to hear what the magic smoke is doing.... Oh! I just remembered another video by Kreosan, he's that crazy Russian doing crazy electronic experiments... He used a Walkman to achieve the same thing. He showed what you can hear with it in a few things... It's mind blowing if you haven't seen it already! Highly recommended... Since this is a two channel amplifier, it literally has two of everything, and so the same resistor should sound the same on both sides, I believe that you should be able to hear capacitors also.... It's a neat experiment... People don't use signal tracers anymore but they still have their place in electronics problem solving even today.... Direct probing is one thing but AF and RF coupling the device under test is something else that's out of this world! It's basically the quickest way to find intermittent problems because you will hear the device struggling even though nothing is showing up on the scope... I bet that this method will find your culprit!

[@goodun2974]

At the stereo repair shop I work for, we use a Huntron curve-tracer/ comparator; assuming that the device has one good working channel and one defective channel, the Comparator can be used to inject pulses into the "same" component on each channel simultaneously and you look at return signal for each channel on the devices' built-in scope. When you find a component or area of the Circuit where the return pattern is different for one channel versus the other, that's the area you should be examining for defective parts. The unit you are working on does need to be (and *must not be*) powered up for this type of diagnostic testing!

[@int53185]

Powerhouse amp with all those output transistors!

[@donsurlylyte]

you did the whole "scared straight" thing on it!

[@AudioElectronicsChicago]

Miracle happened :)

[@tubeDude48]

Lift the Left-side about 2" and drop it!

[@tonymontana897]

It had a brain fart and now it's feeling better lol !! Anthony, your channel deserves more subscribers. I love tuning in. All the best mate and I hope you hit 100k + subs soon !

[@samuelfellows6923]

Tony Montana - 😂

[@johnsweda2999]

use a non-contact magic probe and pick up RF and IF admissions from each component

[@the-matrix-has-you]

Hi, I have TFM 35x too mines in perfect condition except old lamps burned out. Could you please tell me what is the type of led lamps and ratings which should replace the old lamps. Thanks

[@jebrehbaker8613]

Manuals available on the Carver Site

[@fredyearian4968]

Goop might have been to keep cover from vibrating from magnetic from transformer

[@leekumiega6576]

Yes some petroleum based foam does breakdown that way with age when heated .

[@p31army]

I have one of these 35x amps with the horizontal cap configuration. My left channel is considerably lower and very distorted. Do you have a schematic for it so I can do some troubleshooting?

[@moodyga40]

bob carver makes good amp

[@ProdigalPorcupine]

I would've gone in with freeze spray and heat gun to provoke the failing part into revealing itself.

[@alexanderreyes4153]

Hello, my friend, can you help me, I have a carver, could you tell me the measurements of the three capacitors? My technician said that they altered the equipment and he does not know which are the original capacitors and the thermostat that is on the heat sink of how much degrees will it be? can you help me I would appreciate it, greetings

[@Rucas1973]

Can you use an electronic dc load in resistor mode instead of the resistors as the dummy load

[@zoranstojanovski8407]

What about thermal camera to monitor amp?

[@JWimpy]

If you plug your 'scope into an isolation transformer could you probe across both channels? That would put the 'scope probe outside of the amp ground.

[@xraytonyb]

In this instance, an isolation transformer would not help. The problem is that the ground terminals of each channel of the oscilloscope are tied together. If you connect the ground of each probe to the negative terminal of each channel (left and right), you are essentially tying the two channel's negative speaker terminals together. On many bridgeable amp designs, the positive terminal of one channel is common to the negative terminal of the other. The channels are then driven 180 degrees out of phase from one another so that they are in phase at the speaker outputs. Connecting the negative speaker terminals together could result in shorting one channel out, depending on the design of the amp. It sounds a bit confusing, but I think I go through this in more detail on some of the other Carver videos I did. Hope this helps. Thanks for watching!

[@JWimpy]

@@xraytonyb Thanks for the information. I totally understand now. I have seen amps that had warnings in the manual that the channels must be kept seperated.

[@michaelhaiden6718]

Those old systems were all installed with extra smoke

[@jonathancolling2284]

I had a plotter that smoked itself once and seemed fine afterwards. Someone had tipped vape liquid into it!!! The whole room smelled of cherry's afterwards and when I went shopping I walked behind someone vaping and suddenly realised !!😂

[@repairitdontreplaceit]

i would 100% go over those joints on the output pcb

[@re-livehyd1654]

Good job 👍

[@jamestheonas7831]

about half way through the video is the fluke on dc?

[@philno]

I have no idea how or why, but iv also broken somthing to the point it gave up and just worked... I sure it was a plasma tv that died after a lightning strike, I let the smoke out fixing it . It seemed to just give up with its bullshit and just work, I never did find out why.... lets face it if it ain't broke I'm not fixing it

[@robertcalkjr.8325]

Thanks Tony! That is weird!

[@goodun2974]

These units have weird power supplies, designed to loaf along at fairly low B+ voltages until you crank up the volume and ask them to deliver more power and then the B+ more than doubles. Be very careful, if you slip with your probes you may blow this thing up big-time. I don't particularly care for how they sound anyway, kind of dull and closed-down in my opinion. I definitely do not recommend running them in bridged mono mode, they'll be less stable and the distortion will be at least 4 times higher! Besides, how could anyone possibly need more power than these amps deliver in normal stereo mode?!

[@bixy9347]

The smoke might be magic but it must have come from somewhere.

[@michaellitscher9456]

$5 cold solder joint.

[@chrisvinicombe9947]

That's two big gangs of transistors. Usually only see that type of thing in car amps. What's the power of this amp? Edit ok it's 250wpch I should wait before asking questions.

[@int53185]

250w into 8 ohms 350w into 4. 700w bridged.

[@DAVIDGREGORYKERR]

It would have been better if it was a high power Bitstream chip affair

[@mitfreundlichengrussen1234]

You are in a fight with Murphy. Try to simulate sending/giving the amp back to the owner.

[@diabolicalartificer]

Yeh, tell him it's fixed, give it one last test and it'll fail : )

[@xraytonyb]

Never has there been a more accurate statement on KZbin! ;)

[@timka880057]

I remember these Carver amplifiers. I almost bought one. I bought a Yamaha P2350 for my studio. It's a really good amplifier.

[@seanoxborough410]

Board on the circle so smoked a loint

[@goodun2974]

It appears that you're not using an incandescent bulb as a current limiter in series with the power cord. You should be. Also, when troubleshooting an amp for low power, it is sometimes helpful to check the output at a higher frequency, and also measure the distortion at both low and high frequencies and compare ot to the working channel. By the way, I worked on an amp not long ago where the customer's complaint was "low gain on one channel". It turned that the "low-gain" channel was working pretty much as it should, but the channel with higher gain was defective, it had much higher distortion and 7 volts of DC offset at the speaker terminals ( it didnt have an output relay or any kind of protection circuit to shut it down).!

[@philipw7058]

Anything that smokes in electronics is bad and it is impossible to correct itself,and you have to be a professional and have the tools to find a intermittent problem

[@hughmc5419]

My hunch is your protect relay contacts are carboned and not making .Tap that left channel relay. What are you smoking +~ - + ~ -

[@peterjmcgee4680]

Ooey gooey was a worm a mighty worm was he he sat upon Carver amp the Watts he did not see ooey gooey

[@alexanderreyes4153]

Please brother, it will be that you can help me and give me a gift if you have the diagram of that power, pascq they sold me one that heats up and turns off automatically and sometimes it even burns the sound transients, can you help me

[@pauldavies6037]

Loud speaker and power supply relays often lots of intermittent faults and could be bad solder joints on PCB I dont like the design of these amps no bottom cover have to take the hole thing to pieces to have a good look

[@swinde]

Odds are that the failure is still present, and will rear its ugly head at some future time. Electronics do not "fix" themselves.

[@dtwistrewind7361]

There are quite a few self healing components on the market.

[@jonathancolling2284]

@@dtwistrewind7361 lol

[@buildstoys]

.

[@OrganNLou]

Never really cared for most Carver pieces (complicated circuits, poor quality circuitry).

[@coldfinger459sub0]

Off-camera hearing your diagnostic did you go to a series of using the hot heat gun and then switching to the freeze spray can