Fender Champion 30 troubleshooting help

[phatt]

Well Mr Fahey,,you beat me to it 

The thought crossed my mind also but wondered if the supply was big enough?

27-0-27 VDC should be good enough for the LM3886 but you need a bigger chunk of Alloy to cool it.
IME,, I've noticed Fender have always skimped on heat sinks. :trouble

He has a reasonable picture at the top of this page.
Looks like plenty of room to move inside.

I'd be mounting the NEW power chip on a separate board and just tap off the main board.

Phil.

[nebraskaplayer]

Thanks
Which raises a couple of (more) questions.

To test : 
1. unit powered on
2. NO input? nothing plugged in
3. speaker leads disconnected
4. Each lead (numbered left to right looking at chip mounted to heat sink) from the top of the board is numbered 1-9.)
5. Each will be tested individually for pins 1,4,5,6,9 (tested from the solder points to chassis ground)6. I "tried" looking at what I would exect to see for results on schematic (since my meter isn't autoranging...
-noticed they don't specify dc volts...
Pin 1= ?
Pin 4= -27v
Pin 5= 0?
Pin 6= +27v
Pin 9= ?

If you gentlemen could fill in the ?? above before I test.


Regarding the replacement chip,  it is a US "fender" repair shop,  I need to call and discuss the glut of fake chips before if I order.
I'll have a few more questions regarding front vs. back identification, mica insulator, white thermal paste,and thermal grease, assuming I get that far...

It's not a repair... it's a quest...

[nebraskaplayer]

Went to check on testing method for TDA1514A... pins 1,9,6,4,5 per J.M.Farey, per my post above,
I assumed that I would test each pin to chassis ground, but looking at the spec sheet below, now I'm not so sure.
  It does look like pin 4 is ground?, so assuming chip is isolated ,  it would be the same as going to chassis ground?
I'll hold on until I get advice and don't kill the chip (or something else).

From Phillips spec sheet

http://www.next.gr/components-datasheets/TDA1514A.pdf

[nebraskaplayer]

Opps sorry for the spelling: J. Fahey,

So... Some Sucess!!, as a result of inspecting pins closely for testing and replacement on TDA1514A... I found a cold solder joint on pin/leg 1. 

After all of the joints I reflowed and looked at I never saw these smaller pins as a problem even with the magnifying glass I was using.

So I have virtually all of all humm gone and 0 dvc at the speaker leads,  thanks everyone.

There are still some issues I need to figure out.
1. There is no reverb.
2.  Trying briefly input jack 1 and 2 and the gain/volume impact seems off or wrong ...  but the clean (on channel 1) I think seems OK with enough volume for a small amp..

I need to look at those and do some basic trouble shooting on those before I bother all of you on those items.

Should I continue on this thread, or start a new one (if needed for each of the other problems I discover?>?)
thanks again, great help...

Dave

[JHow]

Cool.  I love an inexpensive solution.

[J M Fahey]

GOOD !!!!!!  :dbtu: :dbtu:
Joecool was right after all !!
I asked you to measure those voltages (measured relative to ground if nothing else specified) because I was not happy with the voltage results.
With a  blown TDA1514 I expected to fin a higher voltage, even +/- 27V (the full rail voltage) or thereabouts at the output pin.
Or less than 100mV on a healthy chip.
3.5V were strange, that's why I asked for those measurements.
Why?
Because most SS power amps (specially chip amps) are nothing more than a "big" Op Amp.
And they faithfully amplify whatever you feed them on the input pin (in this case pin 1).
So if for some external malfunction you have 3.5V on pin 1 ... you´ll have 3.5V on the otput pin ..... which is exactly what happened.
You had 3.5V on pin 1.instead of 0 or just a couple millivolts because of a cold/bad solder which did not let it be referenced to ground.
Also causing hum problems and such.
Funny thing is, if you had mounted a new TDA1514 there, it would have worked perfectly ... because it would be hand soldered  :lmao:

[phatt]

Great news,
Re the cold solder join.
I wonder if this is due to the RoHS solder that has been forced upon us? :grr

I've seen quite a few boards that show shrinking issues, especially on warm to hot running components. Some reading reveals that some military folk are fully aware of the high failure rate on this inferior product. Refusing outright to use it.

At the moment I'm still able to purchase Lead Solder where I live but that may change in the future.
Phil.

[joecool85]

So... Some Sucess!!, as a result of inspecting pins closely for testing and replacement on TDA1514A... I found a cold solder joint on pin/leg 1. 

Ah, I thought you had already reflowed ALL joints as I mentioned quite a while ago.   :trouble

On amps like this it is best to just reflow them all then to try and do "just the ones that look bad."  Trust me, none of them are that good.  Honestly, it might take you 30 minutes to reflow every single joint, but it will most likely save you hours or days of troubleshooting.

Glad you got it mostly working though  :tu:

As for the reverb not working and other issues, go ahead and leave them in this thread as it is a generic troubleshooting thread anyway.  Plus it's easier if it all stays together in one area. 

Now, go reflow EVERY solder joint carefully, then let us know if you still have issues and we'll go from there.

Joecool was right after all !!

Don't act so surprised!

Great news,
Re the cold solder join.
I wonder if this is due to the RoHS solder that has been forced upon us? :grr

I don't think it is a direct correlation.  I think it's more that the RoHS stuff is a little more picky on how you solder with it.  When done by hand it appears to me that it is just as good as a lead solder, just more difficult to do.  It may be true that when done by robot they just aren't as good.  It doesn't flow as readily and takes more heat, set times take longer too so everything has to stay very still.  I think this has to do with the higher silver content.

[nebraskaplayer]

Excellent forum,  you folks really go the extra mile in helping the newcomer,

joecool... RE-Looking at your post you did say ALL and that you had seen instances where a few WERE bad but... 40-50 COULD cause problems latter... AHHH...makes so much more sense now, I should have paid a little closer attention.
Plus I was really scared of damaging the chip ...

JM Fahey... Thanks for staying on the low DC voltage at the chip... that finally got me back to it, and the actual problem. (and the picture resizing program)

Tonyharker... early on for link to schematic

Phatt and Jhow... your specific directions for test points and values  kept getting us back to the root cause...   I did try the plastic "chop stick"  pressure on the board to find any changes,... but with the heatsink bolted to the chip obviously didn't get any movement. I also appreciate the resizing and mod program for pics you provided.

A little board protocol, since I've asked so many questions, I have enough posts (although they are all questions, not help)  I can "award" chips... should I do so for above the help received?, or is that something reserved for "regulars"?

I'm not going to spend a lot of time of the Input 2 volume, as I did research and discover it's a darker channel for active pickups and I'm testing with a cheap Fender Tele.

I am going to look at reverb, as I like a touch when playing,  It has spring reverb in a "cardboard"  pan (see pic below).  (I do think I had some reverb day 1, with the pot  very noisy, but it was hard to tell as lound as the hum was previously. Physically it seems that is the only control pot that turns with no physical resistance, which I understand is very subjective).

I did a quick resistance test  of reverb pan input and output wires, R/B was 202ohms, and G/G was 27, I tested another Fender SS with a physically similar size, and it tested virtually identical at 202/28.

I tried to test millivolts at TP13 and TP14 on a 4 vdac scale and got .095 at TP13 and .004 at TP14. converting that gives me 95 millivolts (s/b878m, off by a factor of 10?) and 4 millivolts (s/b >5m, close).  That was with amp on, no input, reverb at midpoint on control.

I also need to put thermal grease back on between chassis and heatsink and spacer?,  any recommendations or cautions?, It was a clear almost like vaseline with just a tiny amount between each.

I haven't pulled the board again (or reflowed anything...yet),  I want to play it a day or two to see if it holds up.

Dave

[JHow]

nebraska player:  Footnote #5 at the bottom of the schematic has instructions for measuring AC voltages.  You need 1khz signal, 8ohm load, various settings...otherwise the readings aren't going to match TP.  you can probably fix this too with out worrying about the AC.  If you have no verb at all I would start looking if U4 and U5 have necessary voltages.  I'm guessing you re-soldered those guys too?

[phatt]

Hi nebraskaplayer,
                         Re Reverb, Simple test no teck required;
Turn the rev knob up full ,,Now bang on the cardboard.
Do you hear any boyoying?

If you do then you know the Pickup side of the reverb works fine.
If nothing,, or very low sound then the PU side of the circuit has issues.

Not much point playing with the driver end until you know the PU side works.

Re points,,,, feel free to click a few for those that help.

Frankly I don't worry much about it as I prefer to thank on a more personal level.

Just for the record,,, There are some incredibly talented folks who frequent this site and I'd like to thank Them for their input into helping those of us with lesser experience.
(Which of course includes Me,,, LOL.)
Phil.

[joecool85]

I would get some thermal paste between the chips and heatsinks before playing too much or you could fry them in short order.  No more than a minute or two of play time at low volume I would say if you don't do the thermal paste.  As you've found, sometimes these chips can be expensive to replace, no point in possibly wrecking them.

[nebraskaplayer]

I won't get back too it until later this weekend.

1. Thought you all may find another SS amp I have interesting... hopefully from what I've read I never have to ask for help on this one, as I understand they can be a bear.

http://entertainment.webshots.com/album/573733998UhWDVL

2. I may be mixing terms up here,  I didn't demount the chip so the white thermal "paste" is still between chip and heatsink.  When I first took apart there was a block of aluminum between, L shaped aluminum that chip is mounted to (with the white thermal "paste"),  but between the block and the L shaped aluminum, and the block and the metal pan, there was the "Vaseline" style grease.  I have seen some other reverences to late 90's Fender solid state amps having it but not what it is or replacement options...,   Almost seems more like a dielectric grease to just prevent corrosion on aluminum to aluminum and aluminum to steel?.

3. I wasn't getting any of the traditional "bong" from anything I was trying, but it was only for a couple of minutes,...  and I haven't reflowed everything, so I don't want to get to carried away until I get that done. ...  (also I need to move everything from the kitchen island... )

[joecool85]

2. I may be mixing terms up here,  I didn't demount the chip so the white thermal "paste" is still between chip and heatsink.  When I first took apart there was a block of aluminum between, L shaped aluminum that chip is mounted to (with the white thermal "paste"),  but between the block and the L shaped aluminum, and the block and the metal pan, there was the "Vaseline" style grease.  I have seen some other reverences to late 90's Fender solid state amps having it but not what it is or replacement options...,   Almost seems more like a dielectric grease to just prevent corrosion on aluminum to aluminum and aluminum to steel?.

As long as you didn't remove the chip from the heatsink, you are good.  If there is a bracket that attaches the heatsink to chassis, I wouldn't worry about putting any "goop" on it.  As you have guessed, most likely it is just dielectric grease.

[nebraskaplayer]

Done !!! (I think).

Thanks for clarification on grease...

So , the reverb was a little more work than I thought,
1. Went to reflowing everything...
2. Noticed with the right light, that the pot for reverb was cracked down the back, see pic below,  (by the way, that was one of the two knobs that was missing when I received it, looks like it must have taken a good impact).
Still need to locate a couple cheap push on D shaft knobs.
Pulled pot from board, it tested open.  Ordered new pot... PITA, mini, snap in, Fender proprietiery..., Got new pot today, stuck in board , and expected instant successs,  Nope...
3. If you look at the pic of the cardboard "reverb tank" I posted back on 1/27, I now see the fine wire was broken always, at the time I didn't know it was a wire.
4. Pic below is a closeup of tank fine wire, after I pulled tank (read, cut the double sided tape it was mounted with.)
5. Tried to stretch wire with tweasers to reach the other post to solder ,too short,  unsucessfully I broke it from the post it was anchored too.  Just to see what it would solder like I "pretinned a post and tried to solder and it appeared that the heat from 30w iron  actually melted the wire more before the solder could attach to wire.

QUESTION... anyone have an idea it there is a wire type, substitute that I could play with to try to fix this one?  I know a reverb tank is only $20-30, but so far only spending the $5 on the reverb pot thanks to all of your help, has been very rewarding.

6. I did have a matching dimension and input/output tank from a small Fender 15R that this amp will replace,  that I pulled and installed, although not very "rich", it does the job.
So fixing the old reverb tank would be to stick in the little 15R.

Thank again to all that helped