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Post subject: Blues Jr. with issues, need advice on repair and modding
Posted: Tue Nov 29, 2011 2:37 am
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Hey everyone,

This is kind of long, I'm trying to provide as much detail as possible about the issue I'm having :oops: I have a Fender Blues Jr. that keeps breaking down. I need help on determining where to begin with repairs and also some advice on making improvements to the amp. I'm not sure what model my Jr is, maybe a Hot Rod Jr III? The plate on the back is chrome and says "Blues Jr." Not "Blues Jr III" on a black plate like the pics I see online. Also the control panel is chrome on my amp, not black like I have seen. It does have the "FAT" switch and the serial number is B-386210 if that will help. I bought as new, not used so can't be too old...

Here's my issue. The amp will seem to be fine for 1 week up to 3-4 weeks and then I'll start hearing a slight crackle or popping, doesn't matter if I'm playing or not, I can unplug my guitar and still hear the sounds. It's intermittent, but it gets more frequent/louder over a few days to couple weeks and can eventually get very, very, loud! A few days after the pops begin, the volume will start to drop occasionally, it gets very quiet and the tone becomes thin. The last time it did this I noticed that the power amp tube on the left (if you're facing the back of the amp) was glowing like a X-mas tree bulb when the volume dropped. When the volume comes back up the tube starts to glow normally.

This first happened about a 3 weeks after I bought the amp. Took it back to the shop and they offered to have a tech repair it on their dime since I just bought it. The tech said he found a couple bad solder joints and cleaned everything but that was it. He replaced the tubes and said it should be fine. Got it home and about a week later, same problem. Tried to use it anyway as I needed it for a couple gigs and while practicing one night 2 weeks after symptoms started again, I heard some crackling and then smelled a strong burning circuit smell. Immediately turned the amp off and checked the back to see if a tube was blown or anything obvious. Tubes all looked fine but I left it alone that night. Replaced the power tubes next day with new ones. Seemed to be OK for a couple days, but then I started noticing the volume drop outs like before, not too noticeable at first but by the end of that practice it was severe again. Dropouts seem to happen in random intervals and last about 5-15 minutes every time it happens. The shop would not look at it for free twice so I started looking around online. I read that the Blues Jr. is biased very hot from the factory and so I ordered a set of tubes from a company I like online that had tubes biased to match, just for the smaller tube amps from Fender and others. Apparently this is getting to be a common practice with several manufacturers.

That brings me to now. I thought I was OK with these news tubes as I got 2 weeks of solid play out of them, but last night while practicing I heard the faint pops and crackles and confirmed it still does this even when nothing is plugged in. I know where it leads at this point. I like the tone of this amp for the most part, but I haven't had it function correctly for one solid month since I've owned it! I'm very careful with my gear in general and handle this amp VERY carefully, it's also never been turned up past 4.

Does anyone have any advice on what I should look into first for a recurring problem like this? I had read on another forum that this could be a bad power transformer or tube socket, but I thought I would check here and see what people had to say. I need to repair it and also want to tweak the amp in general to suite my tastes better but would like to know where to start as I will have to do repairs/mods in increments.

I have a family member who has been building and modding his own circuits for many years. He looked it over and while he's not as familiar with guitar amps as he is with pre amps etc, he did say the board is very straight forward and would be no problem at all to work on. He didn't see any visible burning or obvious fried spots on the board, though he did say he saw a few solder joints that didn't look like a good job was done. He recommended I talk to others with experience with amps first though to make sure that whatever he changes is beneficial.

Any advice on what I should have him fix first that would be the most likely culprit? Also any opinions on good mods? I would like to bring the bias down for sure and also would like to make the amp just a little less bright... a tad closer to the old Blues Jr tone. My family member also said that he saw that changing capacitors would probably improve the tone and wasn't impressed with the stock capacitors in the Blues Jr. Any opinions or advice on either the repair or what to switch out for the mod would be greatly appreciated... or even a link to a site that has gone over this stuff in detail would be great! :mrgreen: Sorry about the long post! I know detail is important when troubleshooting and wanted to include everything I could to help. Thanks guys!!! :D


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Post subject: Re: Blues Jr. with issues, need advice on repair and modding
Posted: Tue Nov 29, 2011 3:18 am
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You should find a good tech for waranty. The guy look at your amp is not a tech.

Nothing you can't do by yourself , It void the waranty and need electronic knowledge.
Your amp need a bias cheking on power tubes and bad connexions/solder repair

Good luck


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Post subject: Re: Blues Jr. with issues, need advice on repair and modding
Posted: Tue Nov 29, 2011 9:54 am
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If the shop where you bought it is NOT an authorized Fender repair center, go to another shop. Your amp is covered under warranty and should be fixed for free. It sounds like the "tech" is not authorized, and is trying to get money out of you even though the amp is covered under warranty.


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Post subject: Re: Blues Jr. with issues, need advice on repair and modding
Posted: Tue Nov 29, 2011 2:59 pm
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Thanks for the feedback guys.

Unfortunately I don't think I have an alternative in my area for a tech. I have since discovered that the tech who worked on my amp is the ONLY tech in the area. I live in a pretty rural area and there are only two music stores, both focusing on different things and they both barely stay operational. The tech is an independent who takes work from both places as well as taking work on his own, but there is no one else around here that does anything other than tinker with their own projects.

I live in WV and the service center search on the Fender site says there are no authorized repair centers in my state! There appear to be some in VA, but honestly I would rather try to deal with this on my own rather than working out driving down there around my work schedule during one of the locations open hours. I'm certainly not willing to ship at all. I tried that before with a larger tube amp and not only did UPS break the amp cabinet to pieces while shipping, they also refused to cover the damage and left me and the shop to fight it out, which didn't end well at all.

If anyone has any ideas of what the likely candidates are I would appreciate the info. I don't have a problem voiding my warranty as I plan to have some mods done to this amp regardless which are going to void it anyway. I don't know if the local guy was just being lazy or shifty or incompetent, but I have had more than my fair share of sending various things off to an authorized dealer or service center, only to have them returned with the problem not fixed at all or only partially cured. I trust my family member as much as I trust sending the amp off or more, and he's right here and willing to help as much as needed. He's built his own pre amps, active circuits for bass and guitar, solid state guitar amp, oscilloscope etc from scratch. He rattled off a few ideas of what could cause that kind of issue off the top of his head, but he's also very cautious of doing more harm than good and wants me to check around first as he hasn't gotten into a tube amp in many years.

Any advice at all on where to start from anyone?


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Post subject: Re: Blues Jr. with issues, need advice on repair and modding
Posted: Tue Nov 29, 2011 4:11 pm
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If there are no authorized Fender places in your state then you should contact Fender and ask them what they suggest you do. If that means shipping the amp then so be it. Explain to them you have a guy in the area who is willing to work on it. Give them his contact info so they can look into him if they choose to. It's possible but not probable that they will authorize him to do the work. More likely they will want the amp seen at an authorized repair depot. Do it. Don't try to figure this out on your own. You can easily damage the amp and cause more issues than you already have. The traces and PCBs in those amp are pretty light duty and they won't tollerate much abuse or be very forgiving to a novice making mistakes. It's your amp and you can do with it as you please but I strongly suggest you get it look at by an authorized professional.

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Post subject: Re: Blues Jr. with issues, need advice on repair and modding
Posted: Tue Nov 29, 2011 4:27 pm
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As far as modding the amp, the single biggest improvement you can make to it is to remove all the guts from it and put them into a bigger cabinet. It won't be cheap. Chet Feathers is a forum member here who did a beautiful job on his. There are cabinet makers who specialize in this sort of thing.

http://carlscustomguitars.com/Dovetailed-Pine-oversized-replacement-cab-for-Fender-Blues-Jr-conversioncab.htm

I had a Blues Junior and went to a lot of trouble and a huge expense trying to use custom electronics to fix a mechanical problem. My trials and tribulations can be found on this board if you search a little. Suffice to say I no longer have a Blues Junior but I can tell you this with certainty. The cabinet is the amp's second biggest problem. You already know the first.

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Post subject: Re: Blues Jr. with issues, need advice on repair and modding
Posted: Tue Nov 29, 2011 4:28 pm
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It is an amp very difficult to repair ; PCB very fragile. Look at this video;

http://www.youtube.com/watch?v=h7-Eo9LWQw0


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Post subject: Re: Blues Jr. with issues, need advice on repair and modding
Posted: Tue Nov 29, 2011 4:47 pm
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Schematics:
http://support.fender.com/schematics/guitar_amplifier/Blues_Junior_schematic.pdf

Lots of great info on all things BJr:
http://billmaudio.com/wp/

Going through that many output tubes that work for a while, then have red-Plating and volume dropping, possibly caused by a bias circuit problem. Could be a bad solder connection, or faulty component, among other things.

For some reason, I can't post my whole response. :?

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Post subject: Re: Blues Jr. with issues, need advice on repair and modding
Posted: Tue Nov 29, 2011 5:08 pm
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Ravenant211 ,one easy thing you can do is to clean tube's contact and socket.

Tubes must be cold, amp unpluged; remove each tube , spray contact cleaner ( without lubricant) on tube's pins. Plug / unplug tubes 5 times. This should clean the contact.

Your amp is not old and contacts have no reason to be dirty ot oxidized. But today we never know the quality of metal part.

Good luck


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Post subject: Re: Blues Jr. with issues, need advice on repair and modding
Posted: Tue Nov 29, 2011 7:03 pm
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Thanks for the info guys!

I will try the contact cleaner option as a potential easy fix, can't hurt, and see if that helps. If not then I have some info to go on to start at least now. I checked out that video and honestly, at least at first before the drop outs start, my popping issue sounds a lot like that guys does. Maybe the sockets are too loose and arcing my tubes to death? I know when I switched them out I couldn't believe how much wiggle they had! In my larger tube amp, the tubes set in the sockets so tight that I'm always afraid I'm going to break them off pulling them out! I think retentioning the sockets would also be a good first option for repairs.

I do understand and appreciate the advice about getting a certified tech to do the repairs... It makes sense and is definitely the safest bet. To be honest though, I just absolutely refuse to ship this amp anywhere. My larger tube amp is the one that got busted last time and I ended up having to fit the whole bill to repair it because everyone washed there hands of the blame. My only recourse was to sue the shop that did the repair for faulty packing (so said UPS) but the amount was hardly worth that much trouble so why bother? All said and done that whole mess cost me double what I bought the amp for and that was with me saving money by building the cabinet portion myself. Especially considering all the warnings about how fragile this amp is, I don't trust it to be handled by any carrier.

I'm also somewhat jaded about warranty repairs in general. I've probably had 6 or 7 things break down on me over the years that were under warranty and only one of those items was truly fixed by the company. I've found that companies are very reluctant to do a second repair, especially when it just came from their facility, even if I obviously had no time to use/break the item again. It's always the blame game at that point and usually ends up going no where so in general I tend to ignore warranties as a waste of time unless the item is very expensive... then I buy a no questions asked additional warranty that usually means just getting a replacement rather than getting it fixed. I just don't want to fool with the process and headaches warranty repairs always seem to bring me.

Bill M's site is awesome! Looks like he's thought of every mod I wanted to do! I believe after trying some of the thoughts suggested here, I'm going to spend about $100-$150 between the mods Bill has available and upgrading the various components that are on the low end side in the amp I'll be golden! Bill's mods replace most of the suspect parts for my problem anyway, so it's partially killing two birds with one stone. Even if I need to change speakers and up the size of the cabinet later (prefer not to, bought the amp because it was small), it looks like a lot can be done to make this amp shine. Worth a shot anyway!

I'm gonna let my guy handle this stuff. I know no one on here knows him, but trust me, he's far, far from a novice and has done some crazy stuff with circuit boards that are more delicate applications than this amp. He's been doing this stuff for 30 years for the fun of it, and he's very knowledgeable and good at it. He just hasn't been inside a full tube amp for about 10 years or so, didn't have a reason, so he thought it would be better to get advice from those who are more up to date with what goes wrong with them first, might save some time and money were his thoughts... He has no doubts though that he can do the repairs required and I don't doubt him.

Really appreciate it guys! Especially the link, great find! If we end up pin pointing the issue I'll post the info back here on the boards for the benefit of others. I'll also let everyone know how the mod situation goes after we complete it! :mrgreen:


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Post subject: Re: Blues Jr. with issues, need advice on repair and modding
Posted: Tue Nov 29, 2011 7:49 pm
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Here is my Blues Jr. The chassis is unmodded. This cabinet is Walnut and holds 2 12 Scumback Speakers.

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Post subject: Re: Blues Jr. with issues, need advice on repair and modding
Posted: Wed Nov 30, 2011 1:05 am
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My first Blues Junior never gave me any problems. My second one (bought in 2009 I think) had a problem with bad tube sockets that wouldn't hold the tubes securely. This caused an intermittent problem with noise and crackling sounds. They were those black plastic sockets, and I read that a lot of other people had problems with them... either Fender had a bad batch or they're just crappy (my guess). My sockets were replaced under warranty, and the amp was fine after that.

I considered trying to retension the sockets, but felt that there should be no need to do so on a new amp. If the tubes are loose in the sockets and you're planning on modding the amp (thus voiding any warranty), I'd suggest replacing the tube sockets with higher quality ones. BTW, I'm no amp tech (far from it!); just relating my experience since my problem was similar.


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Post subject: Re: Blues Jr. with issues, need advice on repair and modding
Posted: Wed Nov 30, 2011 3:54 am
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I checked out that video and honestly, at least at first before the drop outs start, my popping issue sounds a lot like that guys does. Maybe the sockets are too loose and arcing my tubes to death? Ravenant211

___________________________________________

Good cleaning first and if not better after , retension socket contacts. Arcing like we saw in vidéo is a bad contact between tube and socket.
Heat and high voltage oxyde ( insulation between ) metal.

As I say before, today we never know if product ( tubes's socket here ) are always well made. Builder choose low cost parts first.


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Post subject: Re: Blues Jr. with issues, need advice on repair and modding
Posted: Wed Nov 30, 2011 10:28 pm
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Think Floyd wrote:
... My second one (bought in 2009 I think) had a problem with bad tube sockets that wouldn't hold the tubes securely. This caused an intermittent problem with noise and crackling sounds. They were those black plastic sockets, and I read that a lot of other people had problems with them... either Fender had a bad batch or they're just crappy (my guess). My sockets were replaced under warranty, and the amp was fine after that....

Sounds like a perfect example of Arjay's Bruce Zinky quote in his signature / tag line.

I'm so glad I'm not a participant in those adventures anymore ...... although ... the one thing I can say is that my cream board BJ was prolly a lot tougher than the new ones out now by the sounds of things. I know I was a little ham fisted with it on several occasions and I only ever had to repair one trace on the board. I repaired it with the help of Mr. Machrone, of course, because that was a little outside my comfort zone at the time.

Who am I kidding? It still is. :lol:

:mrgreen:

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Post subject: Re: Blues Jr. with issues, need advice on repair and modding
Posted: Thu Dec 01, 2011 12:12 pm
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I had the same problem with my Blues Jr. I brought it back where I bought it from and they called Fender. The amp was still under warranty and Fender said they had problems with the boards in these amps and changed it free of charge. The amp works fine now, good luck with yours.

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