Fender Jazzmaster Ultralight Schematic

**Wildcat** · 07-01-2013, 01:04 PM

Fender Jazzmaster Ultralight Amplifier Problem Solved

**jorgemg1984** · 07-01-2013, 02:44 PM

I had buzzing issues with mine: new electrolytical caps and some wires moved solved it. Good luck!

**AlsoRan** · 07-01-2013, 03:39 PM

Thanks for sharing your experiences, guys.

I will be watching out for these issues and will make darn sure I don't unplug my guitar with the amp running.

**Wildcat** · 07-01-2013, 06:29 PM

Gentlemen, thank you for the help. Yes, I am never going to plug the cord again or put it in after the amp is on.

**ooglybong** · 07-02-2013, 02:44 AM

Sorry to hear about your problem, but thanks so much for the heads up. Although I don't normally do this as a rule, sometimes I can be a bit lazy and 'sneak' a guitar swap, etc. just as you've described. YIKES. Never again.

Hopefully, you can get your amp back to peak operation soon. They're such great amps. Please do keep us updated.

**TieDyedDevil** · 07-02-2013, 03:13 PM

I'm sorry... Maybe I'm dense, but I'm having a hard time grokking what happened.

You unplugged your guitar, got some buzz from touching the tip of the plug, and suddenly your amp stopped working...? Is that correct?

**DRS** · 07-02-2013, 04:14 PM

I've never heard of damage to an amp by either having the input to the amp left open - ie: cable not plugged into the guitar, or the input shorted. Sure it makes a hum when you short it but not permanent damage. Is this something new for this SS amp?

**Wildcat** · 07-02-2013, 04:16 PM

The one end of the guitar cord was plugged into the amp with the other end not plugged into the guitar. That end touched or grounded on something on the floor with a loud pop/bang from the amp. Now the clean channel has a fuzzy buzzing distorted sound while strumming the guitar. I have done this before with cords and the loud pop/bang but never effected the amp. I have taken it to a local Fender Authorized repair shop. But she's not under warranty. I will update you all when I get the word on what might happened.

**docbop** · 07-02-2013, 07:15 PM

Originally Posted by Wildcat

The one end of the guitar cord was plugged into the amp with the other end not plugged into the guitar. That end touched or grounded on something on the floor with a loud pop/bang from the amp. Now the clean channel has a fuzzy buzzing distorted sound while strumming the guitar. I have done this before with cords and the loud pop/bang but never effected the amp. I have taken it to a local Fender Authorized repair shop. But she's not under warranty. I will update you all when I get the word on what might happened.

I've unplugged and plugged in guitars to amps for decades and no problem, maybe not recommended but no issues. I would say you probably had a lurking problem and this pushed over the edge. Finding good tube repair is easy, but finding good SS repair is tough takes more expertise and test gear to do SS.

**Wildcat** · 07-03-2013, 08:25 AM

Yes I agree about the lurking problem as the power up light had blinked off and on in the recent past. Never saw that before and thought it was some sort of internal reset for the amp.

**ooglybong** · 07-24-2013, 10:49 PM

Originally Posted by Wildcat

The one end of the guitar cord was plugged into the amp with the other end not plugged into the guitar. That end touched or grounded on something on the floor with a loud pop/bang from the amp. Now the clean channel has a fuzzy buzzing distorted sound while strumming the guitar. I have done this before with cords and the loud pop/bang but never effected the amp. I have taken it to a local Fender Authorized repair shop. But she's not under warranty. I will update you all when I get the word on what might happened.

Bump on this from a fellow JMUL owner.
Any more clarification on what happened yet or your repair status?

**Wildcat** · 07-29-2013, 07:26 PM

It's been a month since I dropped it off. No word as of yet. I did tell them that I was in no hurry and the tech is backed up. I trust the store that I dropped it off at, Pittsburgh Guitars and the tech is an authorized Fender repair tech/shop.

**Wildcat** · 08-09-2013, 08:36 AM

I heard from the amp tech yesterday. Two issues.

1. Faulty ROM IC Chip. Fender replaced the part for free to my tech.

2. Blown Speaker. My tech through Fender found one of 2 or so speakers left for this amplifier. Apparently Jensen made the speakers to Fender's specifications.

3. I am also having the C33 cap changed to 4.7 micro/f for the enhanced taper on the volume pot.

Cost: $265 (usa)

**TieDyedDevil** · 08-09-2013, 12:57 PM

Thanks for the follow-up.

Just curious: when you dropped the plug and the amp failed, was the floor carpeted?

**ooglybong** · 08-09-2013, 01:31 PM

Yeah, thanks for the follow-up.

Quite the take-down, though, in the blown chip apparently also blowing the speaker. Yikes.
Best of luck with it from here on in.
Oh, yeah. After you get it back, could you also please report on the new volume behavior? Sounds like a good idea.

**Wildcat** · 08-09-2013, 06:29 PM

Originally Posted by TieDyedDevil

Thanks for the follow-up.

Just curious: when you dropped the plug and the amp failed, was the floor carpeted?

Dropped on an area rug on a hardwood floor.

**Wildcat** · 08-09-2013, 06:35 PM

Originally Posted by ooglybong

Yeah, thanks for the follow-up.

Quite the take-down, though, in the blown chip apparently also blowing the speaker. Yikes.
Best of luck with it from here on in.
Oh, yeah. After you get it back, could you also please report on the new volume behavior? Sounds like a good idea.

I did make the point to ask the tech about the ability to do repairs on it in the future. After telling him how much I liked the amp, he was rather pragmatic when he said they discontinued the model. Anything stock is running out as with the speaker.

The volume mod is from Jorg1984 whom has been a great help with advice on this amp.

**Wildcat** · 08-09-2013, 06:40 PM

Originally Posted by ooglybong

Yeah, thanks for the follow-up.

Quite the take-down, though, in the blown chip apparently also blowing the speaker. Yikes.
Best of luck with it from here on in.
Oh, yeah. After you get it back, could you also please report on the new volume behavior? Sounds like a good idea.

I really do like this amp!!! I want to keep it as it is a design that meets my needs as not only an "all rounder", effects are all I need, the tone is fantastic, the "dirty" channel is the real deal, the weight and size are perfect efficiency. The perfect amp if I dare say, but perhaps to good to be true.

**AlsoRan** · 08-09-2013, 09:12 PM

I was thinking the same thing, Wild One.

There is another amp that I played for Rock and it was heaven from my first note - but that model has a LOT of website traffic for failing, often during gigs.

I guess you can't have it all.

Thanks for the posting the results of your repair and I am also very happy you have your baby back.

Happy playing.

**jorgemg1984** · 08-09-2013, 09:28 PM

Just to say the volume mod is not mine, is from another forum member. I did it (my tech did it actually) and it works like a charm: the volume knob is linear (instead of having 90% of its action between 0 and 4) and stops adding highs as volume goes up. Highly recommended... Also upgraded the clean channel op amps in mine to OPA2134 and enjoyed the result too.

The amp is great... I with the reverb was a little better actually and had an fx loop. But it sounds very warm and tubey, very easy to carry around... Excellent amp, the first amp I had that I REALLY liked. I am only selling mine because my highly modded Henriksen head with a Barb EQ ends up sounding even better and giving me a few advantages (louder at 4 and 8 ohms, much better reverb, fx loop, more eq shaping with mids that actually work on the barb eq an the graphic eq, three different sounds on the barb eq...).

**Greaser** · 08-09-2013, 09:35 PM

Originally Posted by jorgemg1984

Just to say the volume mod is not mine, is from another forum member. I did it (my tech did it actually) and it works like a charm: the volume knob is linear (instead of having 90% of its action between 0 and 4) and stops adding highs as volume goes up. Highly recommended... Also upgraded the clean channel op amps in mine to OPA2134 and enjoyed the result too.

The amp is great... I with the reverb was a little better actually and had an fx loop. But it sounds very warm and tubey, very easy to carry around... Excellent amp, the first amp I had that I REALLY liked. I am only selling mine because my highly modded Henriksen head with a Barb EQ ends up sounding even better and giving me a few advantages (louder at 4 and 8 ohms, much better reverb, fx loop, more eq shaping with mids that actually work on the barb eq an the graphic eq, three different sounds on the barb eq...).

Hey Jorge, have you tried your Barb eq with the Fender? Does the Fender take pedals well?

**jorgemg1984** · 08-09-2013, 09:43 PM

Hi Greaser, there's no point on doing that because the Fender has a blackface preamp... The Henriksen is ideal because it's flat and the amp just "eats" pedals. I tried my Barb EQ with other amps but the Henriksen is perfect for that

Apart from that I used ODs, reverb and delay with the JMUL and sounded very good always. I wish it had an fx loop because I think delays and verbs sound much better in the fx loop. My henriksen is now being modded with one

To my ears the JMUL has the Fender tube blackface sound with some of the "jazz amp" qualities because of the neo speaker and the small cubic closed back cab. It's a Polytone with the mid scoop of a Twin Reverb preamp

**Wildcat** · 08-10-2013, 09:27 AM

Originally Posted by jorgemg1984

Hi Greaser, there's no point on doing that because the Fender has a blackface preamp... The Henriksen is ideal because it's flat and the amp just "eats" pedals. I tried my Barb EQ with other amps but the Henriksen is perfect for that

Apart from that I used ODs, reverb and delay with the JMUL and sounded very good always. I wish it had an fx loop because I think delays and verbs sound much better in the fx loop. My henriksen is now being modded with one

To my ears the JMUL has the Fender tube blackface sound with some of the "jazz amp" qualities because of the neo speaker and the small cubic closed back cab. It's a Polytone with the mid scoop of a Twin Reverb preamp

Thank you for the perspective as I think you overall characterized the JMUL at a level that I can not articulate but do understand.

**ooglybong** · 08-10-2013, 11:30 AM

Originally Posted by jorgemg1984

....I used ODs, reverb and delay with the JMUL and sounded very good always. I wish it had an fx loop because I think delays and verbs sound much better in the fx loop. My henriksen is now being modded with one

Interesting. I'm not too knowledgeable about electronics so please pardon here...
If a Henriksen can be modded with an FX loop, can't that also be done with the JMUL? (I'm assuming not.) What makes one possible for modding and the other (I'm assuming here again) not? TIA.

**jorgemg1984** · 08-10-2013, 09:50 PM

Oh I am no expert don't worry.. I believe both could be modded. The JMUL seems to be a more complicated amp but the schematic is available. I chose to mod the Henriksen because I like the Henriksen / Barb EQ combo better than the JMUL (which I sold today)