Hot Rod Deluxe mods

[Curranproducer]

I was searching on the site and cannot find any specific mod lists for the hot rod deluxe. I got one i want to trip out and make sound better as well. smooth out the gain and warm up the over all tone of the amp. i have 6v6's in this thing, I did not do that and already swapped out the jacks for switch crafts. any ideas will be a bunch of fun!

[xtian]

Jim from Omega is a member. Maybe he will share some of their upgrade strategy.

[Stevem]

The first thing to start off with is changing out that bias pot that always goes open/intermittant for a 20 turn ceramic type trimmer.

Remove the original bias pot and silicone the trimmer in its place once you have hardwired it.
Next changing out all the Linear pots for the volume functions with audio taper ones and moding the tone circuit by placing a jumper across the wiper of the Mid pot (center lug) to its non rounded input lug.

In the power supply you can add another 30 to 50uf 500 volt filter to the first node, in fact many of the original caps depending how old the amp will have started to leak, and even if this has not started they sound like crap if you crank the amp loud and you wind up having ghost notes happening.

If the amp is 5 years or more old and the power supply filters are still the original gray cased ones change them out for Ruby, or bigger money blue cased Atom filters.

Moding a amp who`s power supply needs help is a waste of time so do that first.

Another nice mod to the power supply is changing out the 4 recto diodes for fast recovery types.

[Curranproducer]

yeah I got a rage deal on it because it has bad leaky caps, so I am doing that today!!! what type of recto diodes should I pop in there?! 1N4007 ? I got tons of 400x's laying around from all the pedals I build. I was going to beef the 47uf to 100uf, and MAYBE pop in another one next to it since there is space, and I need to jumper the R70 in there for that to work

[Curranproducer]

OK I dropped in new power caps for the entire amp I. it powers up BUT the out put is way low and distorted but not in the good way, very farty. this sound is on all the channels. I put in 6l6's thinking the 6v6's were bad but still the same sound, thought maybe the PI was funky so I checked the resistors for that and everything is the correct value. any suggestions?

[xtian]

Start by checking your bias voltage, then voltages at all the plates and cathodes. All good? Then start signal tracing.

[Stevem]

I use uf5408 diodes which is over kill and hard to get thru the lead holes on some boards without drilling them out larger so go with the 1 or 2 amp versions.
If you have 380 volts or better on pin 3 and 4 of the output tubes than its a good bet that the OT is toast!

To prove out the OT, set your test meter for AC volts and hook across pin 5 and ground of one of the output tubes, then play the amp cranked, if you read more than 25 to 30 volts the rest of the amp is good and the OT is bad, in fact in a darkend room when playing you should see the glow (not heater) inside the tubes plate structure pick up and glow brighter as the tubes are driven as normal, but a short on the primary side of the OT is loading them down!

[jinx1499]

This seems like the right place to post this...does anybody know a way I can just put a resistor in place of my mids knob and then use that pot for a "cut" like on a vox? I leave the mids all the way up anyways so it would be more beneficial for me to smooth out the top end wit ha knob. Thanks in advance, I've wanted to do this for years!!

[martin manning]

You could do that, but it would require removing the Mid pot from the PCB (PITA) and putting a jumper and a resistor in it's place. Then you'd add a new pot (with solder lug terminals) and a cap for the cut, and connect it up with shielded cable. I would test the usefulness of the cut control, which you could do without any modification, to make sure you really want to go to all this trouble. Perhaps you could add the cut pot somewhere else and keep the Mid?

[Stevem]

Another nice mod is to wire up the Mid pot like a Fender tone stack by just shorting across one end to the wiper. A 30 second mod once the board is backed off.

[groovtubin]

The first thing to start off with is changing out that bias pot that always goes open/intermittant for a 20 turn ceramic type trimmer.

Remove the original bias pot and silicone the trimmer in its place once you have hardwired it.
Next changing out all the Linear pots for the volume functions with audio taper ones and moding the tone circuit by placing a jumper across the wiper of the Mid pot (center lug) to its non rounded input lug.

In the power supply you can add another 30 to 50uf 500 volt filter to the first node, in fact many of the original caps depending how old the amp will have started to leak, and even if this has not started they sound like crap if you crank the amp loud and you wind up having ghost notes happening.

If the amp is 5 years or more old and the power supply filters are still the original gray cased ones change them out for Ruby, or bigger money blue cased Atom filters.

Moding a amp who`s power supply needs help is a waste of time so do that first.

Another nice mod to the power supply is changing out the 4 recto diodes for fast recovery types.

May i add a few things?

make the front end 80`s dumble values w/low cath`s plates( use vishay dales) , hi plates caths sound great too,( use NTE metal film) make R-41 220K/500pf. R-75 to 22K....on OD stage change the 22uf to 1uf....remove R-25 add a .022 Make C-10 a .022.. Regulate the screens w/UF4007 diodes.....Curve the clean pot w/220K....ur now miles ahead of a stock one!

My best, jim@OA

[Curranproducer]

sweet!!! I need to get an oscilloscope to find the output problem, then I will get into modding it, but keep the goods coming, dumble mods sounds interesting,and like it could be a lot of fun!!!

[groovtubin]

sweet!!! I need to get an oscilloscope to find the output problem, then I will get into modding it, but keep the goods coming, dumble mods sounds interesting,and like it could be a lot of fun!!!

SO what is the problem? I have 13+ years t/sg n modding them, not that that`l help, but it might!

[Curranproducer]

well I got this amp on a deal cuz of the output not being loud , and the entire amp is fuzzy or farty sounding, even on the clean sound. So I popped in new tubes, it had been modded to 6v6's so I stuck with that, re-biased the amp, and replaced the bleeding caps.I also beefed up the caps from (3)22uf to 47uf, and from (1)47uf to (2)82uf . the PCB has a slot for an extra power filter cap, and it was a mod recommended from a cool hot rod deluxe web site I found. the was a jumper required on the R70 spot between the big filter caps. so it is still the same sound and issue, I re tension-ed the tube sockets and swapped out every tube and went back to the 6l6 tubes. The main power voltages are all good( about 10-15volts higher) than the fender schematic calls for. I have not done the other 30-40 test points for the amp yet, as a friend of mine who does fix amps pretty regularly said to just break down, buy a freaking scope and start tracing the signal issue that way. So I am bidding on a scope now and hope to work through this amp sooner rather than later. Nothing on the PCB looks burned up or melted, and I have to sit down and check all the test points to see if I cna find anything out there

[cbass]

I'd like to have a scope but I have fixed a ton of tube amps and solid state amps without one.
It's very easy to build a listening probe to track wree your signal is going wonky.
http://el34world.com/Hoffman/tools.htm