Remove Old Caps on Fender Hot Rod Deluxe and install new Capacitors

Thread Starter

Adam Monarch

Joined Mar 17, 2019
45
Hi,

I want to replace the original capacitors on my Fender Hot rod deluxe amplifier and install new capacitors. I am getting unwanted noise which sounds like a unwanted buzz, hum, and oscillation. I did do some research online and understand that replacing these caps are a good remedy for this problem. Also the stock capacitors in the Hot rod Fender Deluxe are very cheap and are problematic.

I want to replace these caps with high quality caps and was wondering where I can purchase higher quality as well as a specific brand name of Capacitors. 47uF, 22uF, 22uF, and 22uF all 500v or higher.
 

Attachments

dl324

Joined Mar 30, 2015
12,677
I want to replace these caps with high quality caps and was wondering where I can purchase higher quality as well as a specific brand name of Capacitors. 47uF, 22uF, 22uF, and 22uF all 500v or higher.
Go to one of the major on-line distributors (Mouser, Newark, Digikey) and use their parametric search engines. Anything they stock should be quality parts.
 

Jon Hoover

Joined Oct 10, 2019
31
Go to Antique Electronic Supply https://www.tubesandmore.com/ and look for the CE Manufacturing, JJ Electronics, F&T or Sprague Atom capacitors. These are all high quality replacement capacitors. You can also use the Illinois capacitors as they are a very good quality replacement cap but not considered "audiophile" quality like the others. A lot of the "newer" Fender amps use the Illinois caps when manufactured. It looks like your amp has the IC (Illinois capacitors) in it. I don't know where you got the information that these were bad caps. They are perfectly fine and I have never had a problem with them. Fender spends millions of dollars on research to determine which components will provide good performance and will last for a number of years. They have a reputation to keep up. That's why they have been in business for about 80 years. You should also check your tubes and verify that none of them have degraded and may be causing the noise. I rebuild lots of older tube amps and I usually use the Illinois caps unless the customer wants the high end (high dollar) caps. Just remember, no matter which ones you buy, electrolytic capacitors will only have a usable life of between 20 and 30 years until they start to degrade. Good luck!
 
Last edited:

wayneh

Joined Sep 9, 2010
17,027
You may have launched me onto my next project.

I have an old Tremolux amp and have been thinking for a long time about recapping it. I just looked it up and was shocked to see Tremolux amps advertised at $2000 on eBay! Is that possible, or are they dreaming? If my amp is worth more than a couple hundred bucks, I'll sell its as-is and buy something modern. I'm guessing recapping might even lower the value?

1614293584453.png
 

Jon Hoover

Joined Oct 10, 2019
31
It only lowers the value for the "tube snobs" LOL! If you use quality components for recapping, nobody should care. Regarding the electrolytics, if you have Spragues in there, try to replace them with Spragues. If you have Mallorys, use the CE Manufacturing caps. They bought all the old Mallory equipment for making the multi-section can caps and they make a very fine product. If you have the old blue Ajax caps or the brown turd foil caps, you can replace them with Illinois or Sprague foil caps. Whatever you use, it will improve the sound and reliability of your amp. I always try to change out the 68k and 1 meg input resistors with 5% metal film resistors to lower the noise floor too. Don't forget to change out the bias cap too. Try to leave the bias rectifier alone if it is still good. Lots of the older ones are germanium which have a different forward voltage drop then the newer silicon ones. Also, remember that the asking price on eBay isn't always what they are actually selling for. Lots of people out there think that just because it's old, it's worth 10x more than it actually is. A blackface Tremolux recently sold for $1200 on eBay. That one was modded to add reverb and a few other things. I would think that an all original, pre CBS, blackface tremolux in very good condition would be worth about $2000 to the right person so you're not too far off on the estimated value of your amp. Another thing to consider is, if it goes to a collector, it may never get played. If it goes to a player, they will want something that works properly and is reliable. My suggestion is to find a good music store in your area that deals in LOTS of vintage equipment and ask their advice. See if they think it would be more valuable if left as-is or if it would be better to restore it. Don't go to Guitar Center and ask them. Last resort, if you want to sell it to me for a couple hundred bucks, I'll buy it in a heartbeat!
 

wayneh

Joined Sep 9, 2010
17,027
I've fallen into a rabbit hole.

There are endless sites out there offering schematics, diagrams, common mods, reviews, and on and on. Intricate details about the wood, the covering, the cloth mesh. Mine is the preferred AB763 circuit. All these years, I thought an amp as old as mine had little or no value. I might have been afraid to perform with it had I thought otherwise!

I changed the cloth on my speaker cabinet because I thought black looked cooler. There may have been a cat pee issue as well. Maybe it was years of (someone else's) cigarette smoke that gave it that distinctive reek. It'd probably be worth more if I hadn't done that. Oh well, that was over 40 years ago and there are plenty of other things I could have done better.
 

Thread Starter

Adam Monarch

Joined Mar 17, 2019
45
I was wondering what kind/namebrand of adhesive that would be good for using mounting the new capacitors to the pcb board?
Can I use Goop or a hot glue gun. Also what is the best way to remove the old glue before mounting the new capacitors ie Exacto Knife and rubbing alcohol?DSCN3235.JPG
 

Yaakov

Joined Jan 27, 2019
2,358
I was wondering what kind/namebrand of adhesive that would be good for using mounting the new capacitors to the pcb board?
Can I use Goop or a hot glue gun. Also what is the best way to remove the old glue before mounting the new capacitors ie Exacto Knife and rubbing alcohol?
Usually, there is no adhesive on components unless they are expected to undergo physical shock or extreme vibration. I can't see, from your photo, any obvious adhesive, but if they are glued in maybe it is because of microphonics (?). In any case, not knowing what sort of adhesive is in use it's hard to tell how to remove it.

My suggestion for an adhesive is electronics grade silicone adhesive. the best and most expensive is "DOWSIL", which comes in various grades, but any "neutral curing" RTV will be OK. The last part is critical. Ordinary RTV produces acetic acid as it cures which can damage boards and components. Silastic, which is the DOW brand for this stuff, is what is used in industrial applications and it great.
 

wayneh

Joined Sep 9, 2010
17,027
I don't see any adhesive either, but of course it could be hidden underneath the caps.

In my experience, if the adhesive is old and hard, it usually lets go fairly easily. In other words, careful brute force works fine to free the component, followed by a little clean-up with a knife. If the old caps don't let go at a comfortable level of force, I'd try warming things up with a hair dryer or the tip of a glue-gun if you can get at the glue. It's not always thermaset glue, but it makes things easier when it is.
 

Jon Hoover

Joined Oct 10, 2019
31
I wouldn't use hot glue. It's messy and it never seems to stick where you want it to. It could also melt some of the plastics used on components. I agree about using a clear RTV type silicone cement. I have used generic type in the past with no issues but I agree that the acid that is produced (vinegar smell) during curing could possibly damage things. When it comes to removal of the old stuff, I use a small screwdriver or pick and just keep working at it until it's clean. I have seen a few different kinds of OEM component glue. I have seen hot glue which is fairly easy to get off. I have seen a rubber cement type that sucks to get off. And I have also seen the RTV type which isn't too bad. It might just peel up or it might have to be removed in layers. I wouldn't recommend using any chemical removers like Goof Off or any solvents as they might eat away at your circuit board and damage it. Rubbing alcohol would be fine to use to clean up after removal. Just be patient when removing the glue and pick/cut/peel it off a little at a time. It's tedious work, but it prevents lots of potential damage to your circuit board.
 

Thread Starter

Adam Monarch

Joined Mar 17, 2019
45
Repair Fender Hot Rod Deluxe 1995

Hi I replaced the Illinois capacitors with Fromel capacitors. When I plug my guitar into the amplifier input I get a tone oscillation around 2.115 KHz which I had before replacing the Illinois Capacitors with Fromel Capacitors. When the guitar is not plugged into the input of the amp there is no oscillation. My 3 single coil G&L pickups which I installed into my fender 10 years ago have the oscillation. My Les Paul, 1980, I bought in 1991 has the oscillation too on the bridge pickup. The Les Paul does not have any oscillation on the neck pickup. The neck pickup is a stock pickup and the bridge pickup is a semour duncan pickup. My Squire Strat has a very low oscillation of 2.115 KHz.

The Fromel capacitors do make the amp sound more clean despite the oscillation at 2.115 KHz. My apartment does not have an Oshea Ground aka 3 prong outlet. Also I have a Simmons Solid State wedge amplifier which has the oscillation as well as a Vox
Lil Night Train. My G&L Legacy has fender laced pickups and has less gain due to the fact that I lowered the Fender Laced pickups approxiately 1/2 inch from the strings.

Please let me know what you think.

Thanks,
Adam
 

Ylli

Joined Nov 13, 2015
1,027
I wouldn't use hot glue.
Hot Glue really isn't even a 'glue'. It is more a filler that molds to irregularities in the items being 'glued'. It sticks to thing for the same reason two sheets of glass stick together, there is no adhesive properties involved.

Removing the old glue: A *blunt* knife or other item. Using an sharp knife such as an Exacto is almost guaranteed to damage the board. If the old glue does not pop off easily, add heat.

Reglue with clear *electronics grade* RTV as mentioned above. Use sparingly - glue glopped outside the component footprint is not holding anything.
 

Jon Hoover

Joined Oct 10, 2019
31
Sounds like feedback to me. If you are turning the input gain up and sitting very close to your speaker, your guitar pickups will act like a microphone and you will feed the sound from your amp right back into your amp. Using outboard FX compressors cranked up too far will also give you too much gain and will cause the feedback you describe. Lowering the pickups with respect to the strings will not lower the "gain" of the pickups. It only lowers the effect that the strings have on the pickups. The pickups will still have the same amount of "gain". Referring to the "gain" of a pickup isn't really even the correct term. It's properly called sensitivity. Gain is a term that corresponds to either an amplifier or an attenuator. Amplifiers increase gain. Attenuators decrease gain. Old pickups with loose windings will exhibit more microphonics than pickups with tighter windings. My solution would be to make sure you're not turning up any FX pedals too much to try and get extremely high gain. Maybe turn down the amp or move farther away from your speaker when you play. I don't think it's your amp malfunctioning. I believe your just running with excessive gain and causing feedback between your guitar and amp.
 
Last edited:

Thread Starter

Adam Monarch

Joined Mar 17, 2019
45
Sounds like feedback to me. If you are turning the input gain up and sitting very close to your speaker, your guitar pickups will act like a microphone and you will feed the sound from your amp right back into your amp. Using outboard FX compressors cranked up too far will also give you too much gain and will cause the feedback you describe. Lowering the pickups with respect to the strings will not lower the "gain" of the pickups. It only lowers the effect that the strings have on the pickups. The pickups will still have the same amount of "gain". Referring to the "gain" of a pickup isn't really even the correct term. It's properly called sensitivity. Gain is a term that corresponds to either an amplifier or an attenuator. Amplifiers increase gain. Attenuators decrease gain. Old pickups with loose windings will exhibit more microphonics than pickups with tighter windings. My solution would be to make sure you're not turning up any FX pedals too much to try and get extremely high gain. Maybe turn down the amp or move farther away from your speaker when you play. I don't think it's your amp malfunctioning. I believe your just running with excessive gain and causing feedback between your guitar and amp.
At one time I was using a dbx compressor coupled between the electric guitar and amplifier. The dbx compressor/noise gate had some gain at the output. I no longer use the dbx unit and I am getting the oscillation 2 Khz. Can the dbx unit be the cause of this problem. I don't use the dbx compressor anymore but I am still getting the oscillation.

The dbx is one unit with two channels. I only use the left channel of the DBX266xl compressor/gate.

Thanks
 

Attachments

Jon Hoover

Joined Oct 10, 2019
31
I have never been a fan of compressors used with guitar amps. Many players have trouble setting them correctly so they smooth out their playing without over compressing the signal and causing other issues. I always believed in practicing your playing technique and smoothing out your playing with good technique instead of using outboard equipment. I am 60 years old and have played guitar since I was 7. I also own a small production company and we do sound and lights for live bands on the weekends. I have seen it all and have helped many players keep their sound and lose their problems. At least the players who are willing to listen and work with me. The best way to figure it out is to plug the guitar straight into the amp. No FX, no pedals, etc. See if it misbehaves like that. If all is well, then add 1 additional outboard unit at a time until it starts acting up. That should help give you a clue as to what is causing your problem. If you are experiencing issues with more than 1 amp, then I wouldn't suspect the amp as the cause of your problem. It is probably one of the outboard units or the guitar. But, you did mention it happened with more than 1 guitar. So I would suspect it is being caused by an outboard FX you may be using. Also remember, just because your pre volume, distortion or drive knob goes to 10, it doesn't mean you will get good results with it set on 10. The increase of input gain from such a high setting that early in the signal chain can also cause lots of feedback. Keep your troubleshooting process structured. Change only 1 thing at a time. Take notes. You'll figure it out.
 
Top