Memphis MC1.4000

[Perry Babin]

That's an MJE182. I don't know if the 3198 will take the load. It probably will but be ready to disconnect the amp if it fails.

If you have a BD139 or a 2SC2690, either would be a better option.

 

[Exbass17]

So are you saying for the MJE172 you would suggest the bd140 tho because I have plenty of those as for the ones you listed I don't have any of those in place of the C3198 NPN BJT

it also appears a 10ohm resistor near by the MJE172/182 has been burned

I have all new MJE172 / MJE182 on order through mouser

I am wondering if I don't have the proper 100 ohm resistors back by the transformers

thanks Perry

 

[Exbass17]

Hey Perry I am pretty sure you was right again on this one with the PS Fets heating up like I mentioned before you said something about there may be a problem with the PS drive circuit because I switched out the MJE172 with bd140 PNP bjt's and the amp seems to be operating like a working mc1.4000 I have laying around here the 100 ohm resistors near the transformers heat up upon start then they cool right back down to the point where I can hold my finger on them that just like what the working amp have I does also the PS fets are cold

 

[Exbass17]

I replaced all bjt drivers (MJE172G MJE182G)2 each but the Power fets appear to be still warming up with nothing hooked up in front of the drivers there are 2 resistors that appear to be burned as well but they seem to be common problem in these amps because my working MC1.4000 has the same burned resistors but it works fine

Also I noticed a 220uf 35w capacitor near by the drivers I replaced that the top appears to be bowed upward but is not shorted the readings don't seem right tho when I try to run volts through the capacitor

Also would you suggest me placing the oem 100 ohm resistors back in I replaced due to the values slightly off the ones I installed read 100.9 ohm but come to find out after researching these I got the wrong resistors which are carbon filmed so I have order some new metal oxide filmed like the original supposively more reliable

 

[Perry Babin]

Heating up? How quickly? How hot?

Photos would be helpful for the components that you're referring to.

 

[Exbass17]

I have been able to mess with the amp alittle bit I dunno how but I have sound with alittle bit feedback like bad ground running through the signal also the PS fets cant warm up with a minute I can hold my hand on them but I don't run the amp long also the last 3-4 PS fets towards the middle of the amp do not appear to be warm at all there cold I am wondering if the resistor might be out of sync they say 101 on top of them but when I tested them they all appear to be 101-101.9 ohm

 

[Exbass17]

the capacitor near the front of the 2nd picture has the center bowed upward like a tip its hard to see in the picture due to the capacitor sitting at a angle

R169 and R170 appear to be discolored so I am unsure of there proper values one reads 7ohm and the other reads 4.5 ohms I tested the same resistors on my working MC1.4000 they even appear to be discolored and the values were the same

 

[Perry Babin]

R170 appears to be a 2.2 ohm. It also appears to have overheated solder connections.

You also need to replace the cap that is bulging.

 

[Exbass17]

are you referring to overheated solder connections on R169 and R170? Yes they have been overheated that was what the drive connections looked like the 2.2 ohm you think reads 4.5 ohm R169 reads 7.0 ohm of course I cant make out the band colors because of the one band being either purple or black due to being discolored the band is purple but not sure

Also I have a working amp identical to this one and R169 and R170 are both discolored as well not sure if this is a common problem with these amps or not

 

[Exbass17]

Kind of curious here Perry the only thing I could come up with near that resistor with that color on R169 would be 4.7 ohm you say R170 is 2.2ohm so these wouldn't be k ohm by anychance do you think would they?

I am having a tough time trying to find 4.7 ohm resistor color coded yellow violet gold gold

 

[Exbass17]

Kind of curious here because I looked over the circuitry on a 4kmcd it has all the same values near the MJE182 MJE172 and the PWM riser card there is 2.2 ohm resistor but right next to that one is a 47k ohm resistor which is yellow violet orange and gold the 3rd band on the burned one is discolored black so it makes it really hard to read

 

[Perry Babin]

Desolder both resistors. If they read the same, you can be more confident in the value.

This is assuming that no one has replaced the resistors previously.

 

[Exbass17]

I desoldered the 2 resistors from the board retested both of them they both are within specs even tho they have been burned I am wondering if they need to be a metal oxide style beings even in my working amp they are burned but that amp works fine this amp appears to be having heated power fets due to bared running there is audio through the amp sounds good just that the PS fets are warming up at idle

 

[Exbass17]

Does anyone know if only half the rectifiers were working if that would cause the PS mosfets to heat up with the amp just idling ?

 

[Perry Babin]

You are going to have to take the time to provide better information if you want help.

How hot?

How long to get that hot?

Precisely which ones are getting hot (list the circuit board designations)?

Which are not getting hot?

What do you mean by 'not working' when referring to the rectifiers?

Precisely which rectifiers are you referring to?

Even with all of this, with no technical documents for the amp, it may be difficult to provide definitive answers.

 

[Exbass17]

I am referring in general I will not power this MC1.4000 amp more then a minute but the Power supply fets (IRFP1405) I would say hot enough to fry them if powered for 5 minutes they can be hot enough to where if I left the PS fets powered for over a minute I am sure they would be untouchable

I was referring to the Fast Recovery Diodes FMU36R and the FMU36S there are 2 of each however the reading don't match up on a diode check also I had a similar issue with a MCD4KW however the lights would dim upon being powered even the lighted Memphis leds for the logo and the power fets would heat up I am just wondering if maybe the fast recovery diodes in general would cause a amps Power fets to heat up if only using 2 out of the 4 half the power being supplied

Wouldn't the fast recovery diodes be in line with the drivers or even the circuit?

I just have a tough time thinking there is a issue with the driver circuit ever since I replaced the MJE172G/MJE182G and a couple metal filmed capacitors near by the MJE172/MJE182 with poly filmed capacitors same values 105J 63 until the metal filmed capacitors I order arrive the amp seems to be putting out clear sound

only issue I see is the amp is getting hot upon being powered up for a short time without anything hooked up no rcas no speakers just idling the PS fets are getting hot doesn't seem right because all the Memphis amps I have ever repaired if fixed right the PS Fets are dead cold when idling even the mcd4kw versions but they use a slightly lower powered PS fets but the MC1.4000 still uses the IRFP360 fets for outputs

Also within that minute of being powered I would say the MJE172/MJE182 bjts get warm but not extremely hot to the point you cannot touch them

 

[Perry Babin]

'The readings don't match' isn't telling us anything. Unless you know that the different readings mean that the rectifiers are defective, post the readings giving the precise probe to pin orientation.

The rectifiers are between the power supply and the audio circuit. The convert AC voltage to DC voltage.

The FETs and the drive circuit may be OK if it would take 5 minutes for them to fail. I'd suggest clamping them to the heatsink and see if the heatsink where they're located gets warm.

 

[Exbass17]

I had some FMU36R/FMU36S left over I found I did not know I had so I went ahead and swapped those out with new replacement with the same results

I will try and remount the board back into the amp clamped down and see if that helps like you suggested Perry
Thank you