Help Fixing a MTX Tunder 302

[Frycztech]

I picked up this amp and got it home and it wouldnt turn on. So I opened it up and see that one cap is blow and the 2 large ones look to be bulging. Need some help on where to start. I took a couple pics.

 

[Perry Babin]

Contact MTX to get the value of the blown cap.

The larger caps are likely OK. It's probably only the plastic cover that's bulging.

 

[Frycztech]

So I can just replace that one cap and I should be ok? Should I test anything else?

 

[Perry Babin]

Not likely but it can't be fully repaired without having that cap replaced.

I don't have any specific information on this amp but if no one else can offer suggestions, post the DC voltage on the LM339 and the TLx94 and I'll see if something looks wrong. Have both B+, remote and ground connected. Copy and paste the following into your reply.

LM339
Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:


TLx94

Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
Pin 15:
Pin 16:

 

[Frycztech]

LM339
Pin 1: 5.09
Pin 2: 5.09
Pin 3: 12.24
Pin 4: 5.30
Pin 5: 7.06
Pin 6: 3.82
Pin 7: 5.27
Pin 8: 0.812
Pin 9: 3.68
Pin 10: 5.00
Pin 11: 3.68
Pin 12: 0.242
Pin 13: 0.231
Pin 14: 5.02


TLx94

Pin 1: 2.56
Pin 2: 2.55
Pin 3: 3.21
Pin 4: 0.228
Pin 5: 1.705
Pin 6: 3.58
Pin 7: 0.225
Pin 8: 12.15
Pin 9: 0.234
Pin 10: 0.244
Pin 11: 12.14
Pin 12: 12.25
Pin 13: 5.23
Pin 14: 5.23
Pin 15: 5.24
Pin 16:0.244

 

[Frycztech]

I found the outside of the cap in the amp. I can read on one side
85 C
S11K
723

Dose that tell you what cap it can be?

 

[JMFahey]

I found the outside of the cap in the amp. I can read on one side
85 C
S11K
723

Dose that tell you what cap it can be?

Those look like temperature rating, some kind of manufacturing code and maybe manufacturing date (week 23 of 2017?) but we actually need the capacitance value, say 4700 or 10000 microfarads (uF) or something similar, and a voltage rating, say 25V or 40V or whatever.
Even better, post pictures of any inscription printed on the plastic sleeve.

 

[Perry Babin]

The amp appears to be powered up and producing rail voltage.

 

[Frycztech]

The inscription on the sleeve is melted. I only see 50v on the other side. I see a similar cap with the same markings and that one says TI 0.47mfd 50V is it safe to say this is the same value cap?

 

[Perry Babin]

Did you email MTX to ask about the cap?

 

[Frycztech]

I haven't heard a response back. Is there a specific email that you know of.

 

[Perry Babin]

Tech support.
https://www.mtx.com/ContactUs

 

[Frycztech]

They replied back saying that it is a MAE005, 0.47MFD 50V electrolytic capacitor.
Would this be a good replacement:
RFS-50VR47ME3#5 Elna America | Capacitors | DigiKey

 

[Perry Babin]

It looks OK.

What is the DC voltage measured directly across the pads for the capacitor?

Did you check to see if the amp was producing audio?

 

[Frycztech]

I get 0.017vdc. I did not check it for audio yet. I didn't want to mess anything up. Should I test it?

 

[Perry Babin]

Confirm that you have less than 1v across the speaker terminals before connecting a speaker.

 

[Frycztech]

So i have audio coming out. I replaced the capacitor with a 50v 0.47uF. When I powered the amp up and was checking the output voltages the capacitor blew up.

 

[Perry Babin]

Are you sure the cap was installed with the proper polarity?

 

[Frycztech]

I believe so the, The lead with the stripe above it i used as the negative.

 

[Perry Babin]

Was the board clearly marked for polarity?

The voltage you read for the cap earlier couldn't cause a 50v cap to fail.

Post several high quality photos of the area around the cap.