Saving Money and Time Before Bringing Your Amplifier in For Service
October 4th, 2016
Disclosure – Amplifiers and many electronic devices are capable of storing potentially lethal voltages even if not plugged into a wall outlet and stored for periods of time. Never disassemble your electronic equipment unless properly trained and certified.
Field Amp Technician Announcements
The following technician notes are now available and confirmed (If you own any of these Fender Amplifier models and are experiencing stated symptoms, please deliver your unit to James Hood Guitar Repair Fender Authorized Warranty Service Center to determine if warranty service is required):
* Bassman 100T – Intermittent operation or no output signal to speaker from tube power amp.
* Bassman 500 220V or 240V products ONLY – T1A fuse blows on SMPS module during power on.
* Bassbreaker 15 – Intermittent, noisy, or failed Gain Structure Switch (S1).
* Bassbreaker 15 – Excessive hum picked up by effects loop when cables are routed near power transformer.
With that out of the way, …Hi! My name is David Nevin and I am the amp technician here at James Hood Guitar. If we haven’t met yet, it’s nice to meet you and I look forward to seeing you around the shop in the near future! A little about myself: I have been working on amplifiers for about a decade, and have experience in music electronics in regard to just about every brand that is out there. I have experience in vintage electronics, keyboard repair and service (Roland Certified, Fender Certified), and pro audio repair, as well. I am married 12 years with three awesome sons and recently relocated to North County from the SF Bay Area at the end of last year to be close to family. I had my own store up North and loved being apart of the music community for many years there. Being so close to the beach and babysitters is definitely an upgrade though, and I’m excited to be of assistance to the music community here in San Diego.
Amplifier Service Defined
One of the things that happens when you bring your amp or pro audio gear to us is an inspection of functionality. We confirm or do not confirm (Sometimes they just wanna work when you bring em in) the reported issue(s) and then, if agreed, will ask for a ‘Drop Fee’. The fee is a discounted pre payment for an hour of service. That service includes full testing, cleaning, deoxidation, lead dress, continuity testing, voltage testing, reseating of any connectors and diagnosis (and even repair) of any lingering issues. Biasing can happen in this time period too if applicable, as well as tube replacement and any miscellaneous hardware replacement we may have on the shelf.
For the purposes of this blog, I want to talk about a couple of symptoms you may be able to address prior to bringing in your instrument, potentially saving you fees and travel time back and forth.
You should be able to apply these suggestions without having to disassemble your gear (check the disclaimer above)
If you are experiencing volume drops, intermittent operation, scratchy knobs or other signal deprecating examples, check to see if your unit has an FX loop, usually located on the back of the enclosure. The FX loop may only defined on the enclosure as a ‘Send’ jack, and, right next to it, a ‘Return’ jack. If so, this may be the problem! FX loops are designed to be a ‘bridge’ between the preamp and the output section of your gear. This way, you can bypass your preamp on your unit and just run the effects and color that you want directly to the output section of your unit. Pretty slick, right? This is also a common point of failure on most modern amps in production both tube and solid state. When oxidation or debris gets into the jacks of the FX loop, they can actually disrupt continuity to the point that no signal will pass, or only a little. If this sounds familiar, I’ve got just the trick to at least rule out whether your FX loop is the culprit or not.
First, a quick warning. Do not use anything other than what I’m recommending for materials to use. I’ve worked on enough equipment to determine what general product is acceptable for these types of exercises, and which can cause more damage. Let’s do a quick materials list of what you’ll need:
-Isopropylic alcohol (not WD40, not rubbing alcohol, … not vodka… nothing other than stated)
-400+ Dry/Wet sandpaper (small squares rolled into ‘cigars’ big enough to fit in input jacks. Do not use a lesser grit. Chunks can pop off inside of the jack making things worse!)
Got everything? Let’s get started! Put the unit on a table or somewhere comfortable and almost eye level for you so you’re not having to over work your back. Position the unit so that the front interface is facing you.
Take your sandpaper ‘cigar’ and dip into the alcohol. Make sure that it is well saturated. Scrub each input jack on the front of the enclosure. Make sure you are going in and out, and not ‘spinning’ the cigar. Spinning can create a tear in the paper and leave debris behind, defeating the purpose of this exercise. When the cigar is removed, 99.9999% of the time, there will be some evidence of corrosion being removed. Black marks and even rust lines should appear on the paper. Turn the amp around and repeat the process on the input jacks on the back of the enclosure. Wait briefly to allow most of the alcohol applied to evaporate. This is a great time to make sure all of the nuts and knobs on your amp are secured tightly, and any dust or dirt on the inside/outside of the cabinet is cleaned off (Simple, light detergent cleaners will do most of the work for you without damaging the tolex/finish, but test a inconspicuous area of the cabinet with the cleaner you have to make sure first). Plug the amplifier in and turn it on!
If the issue has gone away
Great! You just saved yourself some cash and time! Good job! It’s a good idea to keep the unit on for a extended amount of time to make sure the fix stuck. If it returns, you don’t need to repeat the process, there’s likely a thermal issue causing the failure which falls into the ‘bring it to the shop’ category.
If the issue remains
Well, we gave it go. We now know that there is a bigger problem with the amp and it needs to be diagnosed further. You can tell me or your preferred technician that you did go through these steps though… which will help expedite the diagnosis process, at least!
There’s a 50/50 chance that your input jacks and FX loop are the culprit in both modern tube, and solid state units when it comes to signal degradation, so why not give this exercise a try? Also, it is good practice to do this from time to time, even when your gear is fully operational. It’s necessary maintenance that, when ignored, will go awry at the most inconvenient time! I hope this note reaches you in peace, and it was a pleasure writing to you. I’ll post another blog here at jameshoodguitar.com next week around the same time.
If you have any questions, or would like me to blog on a music electronics topic that you’re pondering, email us at firstname.lastname@example.org and I’ll be happily oblige!