![]() ![]() The reason for this turned out to be a lack of local decoupling on the reverb board. The amp needed repair because it was making a strange ticking noise when the reverb was turned up. The clean sounds on both channels are really great. The tube emulation circuit seems to involve distorting a signal transformer. It’s a full solid state oversized 1×12 combo with two independent channels. I’ve seen and played most amps in my career in music retail and amp repair, but this HH amp Repair was a bit of a revelation. If you are in need of a Trace Elliot GP12 repair, please get in touch via the contact page Categories Recent Repairs Tags amp buzzing, amp hum, bass amp repair, crackling noise, gp12SM repair, repair, Solid State Amp Repair, Trace Elliot Repair Note that the image is an old image, not the amp in question, it’s actually When I contacted him again the next month, the amp was still working well, another successful repair! The description of the distortion on the note tail does sound a bit like caps, but the soak test didn’t reveal any problems with them. I avoided this because it adds significant cost and I had no concrete reason to suspect them. The next step in hum busting would have been to replace the reservoir caps. I also cleaned the FX loop sockets because unused FX loops are a prime candidate for noises such as those described.Īs part of a general service I also cleaned the Graphic sliders as there were a few little crackles – nothing to do with the described fault. ![]() Cleaning the IDC fixed this and that connection is now stable. I’ve seen this before with another Trace Elliot GP12 repair Mostly crackles, although there was a slight increase in hum sometimes which matched the symptoms described. What I did find was that one of the internal IDCs was causing audible noises when manipulated. I left the amp on soak test for 2 hours, which involves heavily driving the output stage – this normally shows up faults that are temperature or power supply related. Unfortunately I wasn’t able to replicate the customer’s problem which makes repair difficult, so I took a number of steps. The symptoms exhibited by this Trace Elliot GP12 repair were a loud hum and distortion evident during note decay. If you need a Hot Rod Deluxe Repair, please contact me.Ĭategories Recent Repairs Tags crackling noise, electrolytic capacitors, Fender Repair, filter caps, hot rod deluxe repair, Leaking capacitors, valve amp repair The other thermal ‘weak point’ is the footswitch circuit, which gets the same treatment as the other hot resistors in the LT supply. 2 years later, Axial caps are going the way of the dodo so I’ve switched to using high reliability radial Rub圜ons with a special adapter board (which I’ve made available to others as a repair kit available here). Update Sept 2020: At the time of this post (2018), great quality Nichicon and F&T axial caps were still available. The most important caps are C33 My preferred configuration is:Ĭ33 (overrated by 470V using 2 series caps!)Ĭ31 (overrated by 470V using 2 series caps!) ![]() I overrate all caps significantly The cost increase is only a few pounds but leads to better performance and improved lifespan. I use a mix of quality F&T (German) and Nichicon (Japanese) capacitors to replace these parts and I recommend replacement on all Fenders when I’m already removing the board. In fairness to Fender, there are probably hundreds of Hot Rod Deluxe amps using these caps that are still working, but there are also a lot that fail. Fender use these presumably because they’re the cheapest 450V axial caps around. The second common fault is the grey ‘IC’ (Illinois capacitor) electrolytic filter caps which are prone to failure. On newer amps I can just take preventative action – replace the 5W dropper resistor with a 5W part raised off the PCB with ceramic spacers and replace the replace the zener also raised off the board. On older hot rod deluxe repairs there’s some PCB retracking work to do to repair the PCB damage. The dropper resistors are getting hotter than the power valves! (Update 2020: repair kit available here): You can see the heat issues on this picture, taken with my thermal camera. This heat then causes the copper to delaminate from the PCB, leading to crackles and bangs and occasionally complete signal dropout. Fender create their 16V low voltage power supply from a 33V and create significant heat in the dropping resistors and zener. This powers the opamp driven reverb and effects loop. ![]() The most common fault is the Low voltage power supply (LT supply) failure. The amp has two common faults, which are well documented: Because the Hot Rod Deluxe is the world’s most popular valve amp, I get a Hot Rod Deluxe Repair arriving quite regularly. ![]()
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