Cherry Amp Repairs?

Early B. · « **Reply #20 on:** 3 Jul 2022, 11:29 pm »

Quote from: morganc on 3 Jul 2022, 04:42 pm

I had an issue with mine as well years ago when the two speaker cables hit and shorted.

Same thing happened to me when I owned the STMs!

bobh123 · « **Reply #21 on:** 4 Jul 2022, 05:19 am »

I touched one of the speaker cables to ground and seem to have shorted the output MOSFETs on my one of my 4-Cherry cards; the card says Maraschino Cherry Amp Rev F. The MOSFET part is a B416 made by Alpha Omega Semi, whose site says that part is discontinued. I have found a few suppliers with them in stock.

I was dumb enough to do this twice; Tommy repaired the first one. When a card fails, I hear what sounds like small relay clicking every few seconds; probably a safeguard for power supply since it doesn't seem to have any fuses.

I've read other postings that mention similar symptoms in various models.

Tommy may have had some MOSFETs in stock or some assembled cards in process in Dec. May be difficult to obtain those from his company. If difficult, I'm thinking about ordering some of the B416's and trying them on my card. If successful, I can offer parts to other owners with similar failures/symptoms.

Bob

bobh123 · « **Reply #22 on:** 4 Jul 2022, 05:23 am »

I did a similar sleeve on my bananas; be nice if they were further apart.

Bob

bobh123 · « **Reply #23 on:** 4 Jul 2022, 05:26 am »

Quote from: ealtan on 3 Jul 2022, 10:46 am

Very sorry to see Tommy's passing. Rip... I noticed when my Cherry STM broke, and wrote to Tommy, with no replies then searched what's happening... Now discovering this... I'm without words. I'm searching what to do with my STM. I just happened to take XLR out when it was on... And now there is repeating noise coming from power supply like a car starting engine... But it doesn't work. May be it's just a fuse, i don't know. Either way I'm thinking to sell my Cherry STM (60v). If someone interested, you can write me...

Ealtan: See my posting from a few minutes ago; I have the repeating noise in my when the failed card is installed. Once I removed the failed card, the other 3 channels work fine.

Bob

ealtan · « **Reply #24 on:** 5 Jul 2022, 11:45 am »

Yes Bob, the sound is like what you described, a relay clicking. If there is no fuse, the situation I thought is even worse. The thing is I live in Turkey, so difficult to find someone who understands class d amps... If there is a failed card issue, I'll need all the help. Shorting from a touch of speaker cables is more common. But taking out XLR cable is what I did in all my previous amps. Nothing happened. A disturbing sound from speakers came at most. And I'm seriously thinking about selling it... Considering even sending to somewhere else, all repair, transportation and the extra VAT reduced price...

FL Guy · « **Reply #25 on:** 22 Jul 2022, 06:49 pm »

Likewise I also have a Cherry amp (STM with King power supply) with the clicking noise and no output, in need of repair.

If and when anyone finds either someone capable of repairing this amp, or supporting information so that a non-affiliated repair person can do the repair, I am interested in the info also.

FL Guy · « **Reply #26 on:** 23 Jul 2022, 07:18 pm »

Quote from: bobh123 on 4 Jul 2022, 05:19 am

... When a card fails, I hear what sounds like small relay clicking every few seconds; probably a safeguard for power supply since it doesn't seem to have any fuses. ... I've read other postings that mention similar symptoms in various models.

Tommy may have had some MOSFETs in stock or some assembled cards in process in Dec. May be difficult to obtain those from his company. If difficult, I'm thinking about ordering some of the B416's and trying them on my card. If successful, I can offer parts to other owners with similar failures/symptoms.

@bobh123, It's very kind of you to offer to share the result of the experiment you mentioned, and possibly some parts. if you would, please do let us know how it goes.

It seems that we are most likely on our own in terms of getting these amps fixed, so any info on potential solutions (whether successful or not) would be of interest and appreciated by many owners.

bobh123 · « **Reply #27 on:** 24 Jul 2022, 05:07 am »

Several sites including Alpha Omega confirmed that the FET is obsolete. A few warehouses in China have them. I ordered a bunch tonight. Should be here in 2 weeks. Hopefully that'll fix the issue.
Bob

rhale64l7 · « **Reply #28 on:** 24 Jul 2022, 05:30 am »

Yep that's supposedly the problem with mine. And supposedly they only come in matched pairs I was told. And very expensive.

FL Guy · « **Reply #29 on:** 24 Jul 2022, 02:38 pm »

@bobh123 or others, can you tell us how many of the B416 parts are used per channel? (I haven't opened my STM/power supply case yet to take a look, I guess that I might as well at this point.)

bobh123 · « **Reply #30 on:** 10 Aug 2022, 05:33 am »

FL Guy: Each channel has 4 FET's. I touched one speaker lead to ground which seems to have shorted out 2 FET's.

RHale: Matched pairs are expensive since rarely does a semiconductor manufacturer provide them because of the relatively low volume compare to the quantity made within wafer runs; often we're looking for a pair that was close to each other on the same wafer. Pairs are normally matched by the equipment (amp) manufacturer. Is time/labor intensive, especially if the parts have wide variation in their characteristics necessitating more time to find a pair.

I received 100 of the FET's a few days ago; part numbers on the received parts match what's on my channel card. I will strive to match a pair then place into my failed card; I'm hoping that the shorted FET's didn't take out any components earlier in the signal path.

Will let you know my results, and if feasible for me to match & offer pairs for a reasonable cost.

rhale64l7 · « **Reply #31 on:** 10 Aug 2022, 09:01 am »

Thanks for the reply. I hope it works and you can help others out. Mine will hopefully be done this week.

Thank You,
Ron

FL Guy · « **Reply #32 on:** 10 Aug 2022, 11:41 am »

@bobh123, thanks for the info. @bobh123 & @rhale64l7, I'm looking forward (I'm sure others too) to hearing how it goes.

My case might be slightly different, not certain - mine failed around the time of an electrical storm (different path though of course, so I'm not sure whether it's the same problem). Or perhaps I might have been clumsy and touched a speaker wire to ground but didn't notice it. In any case it has the same clicking sound symptom, so it sounds like the FET(s) are likely at least a problem.

Likewise, I'm just hoping that this works, and no other components were damaged in the process.

RonN5 · « **Reply #33 on:** 10 Aug 2022, 02:55 pm »

I would like to say again that using a binding post sheath such as in the photo below is critical for Tommy's amps.

Many amps have binding posts that are farther apart...or are encased in a plastic housing which makes shorting much more difficult (see photo below). Tommy's amps often have binding posts that are close to each other and not plastic housing so unless you always turn the amp off and wait a few minutes before changing speaker connections, you are at risk.

FWIW, I would say that in Florida, lightning protection, power strips, or unplugging after listening are pretty important given how many storms there are from late may through September.

FL Guy · « **Reply #34 on:** 10 Aug 2022, 02:58 pm »

When time permits, it would be great if someone could post pic(s) of the correct - and genuine, FETs for reference. Thanks!

morganc · « **Reply #35 on:** 10 Aug 2022, 07:08 pm »

Quote from: RonN5 on 10 Aug 2022, 02:55 pm

I would like to say again that using a binding post sheath such as in the photo below is critical for Tommy's amps.

Many amps have binding posts that are farther apart...or are encased in a plastic housing which makes shorting much more difficult (see photo below). Tommy's amps often have binding posts that are close to each other and not plastic housing so unless you always turn the amp off and wait a few minutes before changing speaker connections, you are at risk.

FWIW, I would say that in Florida, lightning protection, power strips, or unplugging after listening are pretty important given how many storms there are from late may through September.

Genius idea! Love Tommy's amps but why didn't he either install a freaking fuse or separate the binding posts wider? Regardless love what you've done!

bobh123 · « **Reply #36 on:** 11 Aug 2022, 09:12 pm »

Ron: After you'd earlier posted your idea about the sleeves, I installed them on the amp terminals. Unfortunately, when I moved the speaker for carpet shampoo'g I forgot to turn off the power and touched the speaker end of the cable to ground. Hence my current repairs.

Ron: Sounds that you sent your amp in for repair. What did you have repaired and where?

FL Guy: Here's pic of one channel card from my 4-Cherry

FL Guy · « **Reply #37 on:** 13 Aug 2022, 11:18 pm »

@bobh123 - great, thanks. That may help folks who attempt to source parts (now or in the future).

RonN5 · « **Reply #38 on:** 14 Aug 2022, 10:43 am »

Bob… I never had to have my 2Cherry repaired. Because I live in Florida with lots of lightening, I never leave the system powered on, so almost no chance for shorting. As for the sleeves, I’ve used those on and off over the years depending on the binding posts of the amp I had at the time… and when I kept reading about Cherries shorting out, it seemed like posting this idea might help others.

bobh123 · « **Reply #39 on:** 24 Aug 2022, 05:03 am »

I went through quite a process to match MOSFET's both for current and voltage to less than 1%. I selected a pair and replaced the shorted pair of MOSFET's; I did not replace the functional pair. The amp works and sounds great.

If you have what sounds like a small relay clicking, that's likely an overcurrent protection in case a channel shorts out. You can easily check by unplugging the AC power plug, removing the top cover and using a DVM to check resistance between the 3 leads on the FET; for my shorted channel, all 3 combos of lead pairs showed a short so was easy to confirm.

If someone needs pair(s) for a channel, I can match more and sell them to you.

For those wanting to repair a unit, realize the MOSFET's are challenging to gently remove without damaging the PC board traces. I may entertain replacing MOSFET's on cards that have known shorted MOSFET's; shipping the card costs less than shipping the whole amp. Most other repairs will be harder without a schematic. Seems to be an FPGA or similar on the board.

Bob