One channel of ModWright KWA-150SE running very hot

stangman67

Not an electronics expert here so seeking advice from the group.

Bought a KWA150SE from TMR less than a month ago. Received the amp with undocumented damage on the right rear corner (pictured below). All seemed well operationally so we settled on a 350$ refund to cover the damage.

Yesterday was the first time I was able to spend a significant amount of time with the amp and I realized the right channel of the amp was running very very hot compared to the left side. I shut it down and powered it back on this morning and let it sit at idle without preamp on.

Temp readings are as follows
Left channel heat sink in middle of heatsink : 74 degrees
Right channel heat sink in the middle of heatsink : 130 degrees

This has gotten me very concerned as something is very much amiss. TMR offers a 45 day warranty on these products but the stipulations are that they or a repair center will repair at their cost but unsure I want to let them try to repair a 4000 dollar amplifier.

Any suggestions, or something I may be missing? Sonically everything seems just fine. I have an email out to Dan Wright to see what he says as well. This is all very disheartening

pitdogg2

Something is wrong. It may need to be rebiased or maybe something was knocked loose (output)

It more than likely needs work

invalid

Try it without the speakers connected to it and just let it idle, see if it still gets hotter on the one channel. Then try it without the preamp connected to it's inputs just to rule out the speaker or the preamp. It's probably a bias problem in the amp, might just need to be adjusted.

Emlyn

It looks like there is a low bias/high bias physical switch on the back of this model and it is a fully differential dual mono design so it has to run evenly on both sides. May be something faulty or just loose but I would not leave it powered up. May or may not be related to the obvious drop damage.

You are right to reach out to Modwright for advice first. Hopefully it’ll be an easy fix.

txcoastal1

Dan will be all over it. he's a great guy and I have spoken and chatted over email many times. Kristin Boyd is also great to work with

F1nut

Sounds like it needs the bias adjusted.

stangman67

Thanks all for the input. Dan got back to me and said the same, but added if it’s been run like this for some time it may need the output transistors replaced as well.

TMR obviously did not do a thorough check before selling this amp and if they did, this is a very neglectful thing to not annotate in the condition report. I am pretty pissed but will give them a chance to make it right on Monday. I’m going to push for them to pay for me to send to MW for diagnosis and repair

maxward

I agree. They should have caught that unless it was caused by the shipping damage.

Clipdat

Was there damage to the cardboard shipping boxes that aligns with where the damage is on the corner of the unit?

stangman67

There was some damage on the cardboard but nothing that would explain the damage on the amp. I have a feeling it was mishandled when packing and that particular employee didn’t own up to it and shipped it out anyway. I’m not all that concerned about that damage, in the rack I will never see it. But the operation issue has me very concerned. It will be on its way back in the next few days and we will go from there

stangman67

Here is the latest reading. Hour after turning on and sitting idle. I turned it back on to take these pictures as proof before I sent it off. TMR claimed they don’t check bias on SS amps unless they see a reason that causes them. The massive heat should have been a clear sign in my opinion.

I will still give them a chance to rebias the amp and make things right before I turn into the guy that bashes them everywhere, as Dan from Modwright has recommended I send it back to them over him as they have a very good tech that will be able to repair it correctly in a much better timeframe then he will be able to. The whole thing has most certainly left a very sour taste in my mouth up to this point though

Emlyn

Is there a high bias/low bias switch on the back of that model and if so does the switch make a difference in the heat on each side?

stangman67

There is a low bias/high bias. It is in high bias but Modwright says to leave it in high bias. I’m sure it would change things, but obviously there is a problem either way, so need to get it dealt with

TEAforONE

Every company makes mistakes form time to time. It’s how they deal with them, that separates the men from the boys. I hope they do the right thing here,and take care of you.

invalid

I wonder how hot it runs on high bias?

Clipdat

stangman67 wrote: »

There was some damage on the cardboard but nothing that would explain the damage on the amp. I have a feeling it was mishandled when packing and that particular employee didn’t own up to it and shipped it out anyway. I’m not all that concerned about that damage, in the rack I will never see it. But the operation issue has me very concerned. It will be on its way back in the next few days and we will go from there

I agree with your assessment. I certainly hope TMR is covering the return shipping for you.

audioluvr

invalid wrote: »

I wonder how hot it runs on high bias?

I'm guessing 145 on the right channel and 101 on the left.

From my limited experience with amps and failure it could be something simple like vibration in transport moved the bias pot (which are usually quite sensitive) or you have a FET that is about to fail (not good) and needs replaced. Just my 2 cents worth

decal

txcoastal1 wrote: »

Dan will be all over it. he's a great guy and I have spoken and chatted over email many times. Kristin Boyd is also great to work with

This is true!!!!

boston1450

Maybe they will send you a new unit back for a happy ending

stangman67

Hahaha that would be a miracle, def not gonna happen. I’ve discussed both with Dan and Peter at TMR, I’ve been assured they will take every precaution and repair/test correctly with guidance from Dan.

CS so far has been great, so happy news there. Only bad part is I will be without tunes for a few weeks but a dude will survive

Oh and while on the phone with Dan, he also managed to sell me on a PH9.0X phono amp. Wasn’t too hard of a sell lol

Mike Reeter

Sorry to hear of this disappointment, this is the kinda thing that keeps one awake at night.

But, I'm positive it will be worked out.

Clipdat

Maybe they could just do a straight up swap with this one they have listed, to minimize your downtime: https://tmraudio.com/components/power-amplifiers/modwright-kwa-150-signature-edition-stereo-power-amplifier-kwa-150se-black/

stangman67

TMR has had my amp back for two weeks now and crickets on the status of repair. Last monday I was told it "would be on the bench in a day or two".

Starting to get bad/scammerish vibes on TMR. They sold a high dollar amp with an obvious issues, are showing absolutely no urgency in conducting or communicating about the status of the repair. I am all about giving a company the benefit of the doubt, but way way too many ref flags on this transaction thus far

pitdogg2

Sad to hear.

Clipdat

I would relay that info to Dan at ModWright.

I'm sure he would like to know about how slowly an authorized dealer of his products are handling a routine servicing.

stangman67

My last email got a response. So at least there is communication. They are saying they might send it back to Modwright for repair. Which I am more than ok with, just means more months without the amp.

Clipdat

Damn. That is frustrating. I still they they should've just swapped it out with that other one they had in stock and then you're back in business and they can fix the other one on their own time. It's their fuckup after all.

stangman67

Honestly if it ends up going back for Dan to repair, I will be a happy camper. It will have a complete clean bill of health and it will make me feel a lot better

Clipdat

Yeah, well said.

VR3

Keep in mind most tmr audio inventory is consignment

Toolfan66

No way is TMR going to scam you or anyone else, I will agree there should be or have been better communication. It should have went straight to Dan in the first place IMO.