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Posted: Fri Aug 20, 2010 12:26 am
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Hi all,

John Fromel here,

The early HRD's had some problems with the power resistors on the 16v rail and problems with the plate load resistors as well.

I think that in a plywood cab the amp would sound pretty decent as designed but Fender opted for MDF for the cab and it makes the amp sound boxy and farty at the same time. not a good combo in my opinion.

If you replace the power resistors with 5w 330 ohm power resistors installed off the board about a 1/4 inch and secured with some silicone and also replace all the plate load resistors you will solve most of the reliability problems with the amp. If you don't want to replace the input jacks it's also a good idea to wrap your guitar cord around the handle before plugging in so if you pull on the cord you won't rip the jack off the circuit board.

If you are looking to make your HRD into a $3000 hand made amp then look some where else. If you want to have a really good playing amp at a decent price then the HRD may be a good way to go. On a side note the HRD is the best selling tube amp of alll time. Even with their design flaws it's a pretty decent amp for the price.

If you are not handy with a soldering iron then please let someone else mod your amp if you want to have it modded. The circuit boards used in the early amps are pretty fragile and the ones they are using now are really good but very hard to remove components because they are using double sided boards with plated through holes.

If you are concerned about your warranty then please to not cut open your perfectly good working amp. Modding the amp will void the warranty.

I am Happy to answer any questions.

THX


Last edited by jfromel on Fri Aug 20, 2010 2:47 pm, edited 1 time in total.

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Posted: Fri Aug 20, 2010 2:34 pm
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Hi John,
This is not the place to advertise your mods or shop.

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Posted: Fri Aug 20, 2010 2:48 pm
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Was not trying to advertise, just answer some questions. I edited my post to remove anything that may come across as advertising.


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Thu Jun 09, 2011 7:14 am
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I think John's post adds greatly to this discussion, and didn't come across as 'advertising.' One poster specifically asked whether anyone had heard of the Fromel mods or knew anything about them. John Fromel's comments were quite helpful.

I have a Pro Junior (not a PJ 3) that is still under warranty, since I bought it only recently, but, get this, I'm in Japan, and it's considered an imported product, so Fender Japan doesn't warranty this amp for five years. It has a ONE year warranty.

Well, been here a long time, and that's how Japanese companies treat warranties within Japan. That includes cars, believe it or not. No such thing here as a 7-year powertrain warranty. Two or three years max.

I digress.

Anyhow, I did order the Fromel mod for the Pro Junior but have yet to receive it. Yes, it will void my one-year warranty. So what. Voiding a five-year warranty would be more of an issue.

If anyone is interested in the results, contact me via this forum in a month or so.


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Thu Jun 09, 2011 8:19 am
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I did end up purchasing the mod kit and liked it so much that I bought another mod kit for my Epiphone Jr.

Very much worth the money and a very clear improvement on sound.

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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Wed Oct 01, 2014 10:29 am
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Hello Fromel, i have a hot rod deville 2x12 and also with a Fromel mod. I`m having the boxy farty issue and i`m considering making a new cab for my HRD. you said:

"I think that in a plywood cab the amp would sound pretty decent as designed but Fender opted for MDF for the cab and it makes the amp sound boxy and farty at the same time. not a good combo in my opinion."

My questions are:

1- Do you think making the new cab of pine wood would be better than plywood?

2- The unusual position of the 2 speakers inside the cab of the Hot Rod Deville do you think is in relation with the boxy farty issue? In other words, do you think that a conventional 2x12 cab twin reverb style would benefit the Hot Rod Deville in the tone department?

3- Have you tried the Hor Rod Deville with another 2x12 cab? Comments.

Thanks in advance


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Mon Mar 20, 2017 11:19 am
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Recently sold an original Hot Rod Deluxe (switched to a Blues Deluxe when I switched to a Tele, found the Blues Deluxe a better fit) that I had modded by a local amp shop. They did a mod almost identical to the Fromel kit (main exception being Switchcraft jacks.)

First, the Mods did not fundamentally change the tone of the amp. It was an improvement, but not the kind you will hear under Volume 2–crank it and you can tell the difference. To me, it was more of an improvement in the feel and response of the amp. I got compliments from other HRD owners about how "quiet" mine was when I was not playing as well as how full the amp was–no brittle highs and no flubby lows.

Second, the amp shop (Acorn Amps) went over all of the solder joints and glued down the capacitors. The mods plus the additional extra steps really made my HRD a reliable road amp. The amp survived multiple trips to Texas and back to Georgia as well as a trip up to New York and back, including an accident where the handle broke and the amp tumbled down a flight of concrete stairs (about 6 steps.)

Third, the easiest way to make this a good amp for bedroom volumes is to replace the 12AX7 for a 12AY7/12AT7 in V1. Not only does this make the amp quiet it also adds some extra clean headroom. This simple and easy swap will fix the way-too-quiet to ear-piercing-loud bedroom practice problems.

Again, I didn't actually use the Fromel Kit for my HRD but the amp shop did the same type of mod. I would recommend this type of mod for the amp for any HRD owner, especially having a qualified tech redo the soldering joints.


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Sat Mar 25, 2017 1:37 am
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If you changed the 470 ohm resistors to 330 ohms, you just made the amp less reliable, as those resistors will produce more heat than before. Not sure how someone came up with that lame idea. :roll:

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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Sat Mar 25, 2017 8:36 am
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shimmilou wrote:
If you changed the 470 ohm resistors to 330 ohms, you just made the amp less reliable, as those resistors will produce more heat than before. Not sure how someone came up with that lame idea. :roll:

Please explain, technically, how you think this happens. P=I^2*R, and unless I (current) changes, going from a 470 Ohm resistor to a 330 Ohm one will reduce P (heat) by 42%.
(Granted, the extra current that passes will get converted to heat somewhere else in the system, whether it's in different resistors, tubes, or your eardrums. But "those resistors will produce more heat than before" seems patently false.)

Also note that resistors are rated for Watt, so it's generally trivial to get one that can handle the heat no matter which way you go.


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Sat Mar 25, 2017 5:40 pm
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Exactly! If you decrease the resistance in a circuit with the same supply voltage, the current increases. Ohm's law really does work. :shock:

I actually use simulation software to illustrate that the heat produced (watts) increases.

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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Sat Mar 25, 2017 6:00 pm
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470 vs 330, note the approx 50% increase in current.

Image

Image

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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Mon Mar 27, 2017 8:21 am
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The extra heat generated is going to be dissipated in the 1N5353 zener diodes. They are also a source of heat related damage to the boards.
Lowering the value of the resistors is robbing Peter to pay Paul.

I use 4 1000 ohm 5-watt resistors piggybacked in pairs in parallel. This provides for a 10 watt dissipation that transfers more heat into the chassis instead of the board.
Glue them down to the board and each other.
I pull Fromel mods to the tone stack. They don't make the amp sound better, just a little different. My mods actually make them sound better. But that's my little secret.


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Mon Mar 27, 2017 9:28 am
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For crowded amps with known heat-prone damage, board issues I've used 10-watt & 25-watt, finned Ohmite resistors attached to metal chassis. Works well on PSU and cathode resistors --- where lead length is not a stability issue.

http://www.mouser.com/ProductDetail/Ohm ... aQodQOAB7A

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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Mon Mar 27, 2017 9:37 am
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TimsAudio wrote:
The extra heat generated is going to be dissipated in the 1N5353 zener diodes. They are also a source of heat related damage to the boards.
Lowering the value of the resistors is robbing Peter to pay Paul.

I use 4 1000 ohm 5-watt resistors piggybacked in pairs in parallel. This provides for a 10 watt dissipation that transfers more heat into the chassis instead of the board.
Glue them down to the board and each other.
I pull Fromel mods to the tone stack. They don't make the amp sound better, just a little different. My mods actually make them sound better. But that's my little secret.


Hello Tim. I live in Venezuela and I made the Fromel mod to my Hot Rod deville 2x12 and is a better amp but still suffering from a very very harsh ice picki highs (still have the gold label speakers). I don't know if is a wrong installation of the Fromel Brightness mod (100pf mica cap across pins 2 and 3 of the volume pot, on the solder side of the pcb)" what do you think?

Whitout the interest of reveal your secret sauce for the tone stack. Is there anithing you recommend for after the fromel tone stack mod?

Thanks in advance. Your comment will be very helpful


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Post subject: Re: Any opinions on the Fromel Electronics HRD amp mod?
Posted: Mon Mar 27, 2017 8:45 pm
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Well, the HRDX uses a stock bright switch that affects the cathode circuit. This type of circuit provides better treble response throughout the volume range.
The Fromel bright circuit at 100pF is a standard Fender accessory circuit that improves brightness at low levels. It has diminishing effect as you turn up the volume. Its effect is gone by 1/2 volume.
It doesn't work as well as the stock bright switch.
If you have ice pick issues, I would remove it.
The main cause of ice pick treble, In my experience, comes from the guitar.
There is a resonant response from all pickups that increases treble output at the resonant frequency.
With Tele pickups, its about 2.7KHz. With Strats, its about 3.5KHz. These are the cause. To remedy the situation, I use a lower value resistance in the volume control of the guitar.
If you have a 1meg, go to a 500K. If its a 500k, go to a 250k. The increased load on the pickups affects the resonant peak more than the overall output. This results in a loss of resonant treble and less blood coming out of your ears.
The Fromel tone stack mods that I have seen use a .015 mid cap and bypass the midrange control to shunt midrange to ground. While it makes the mid control mostly inoperative, the mod is applied equally to Blues Jr and Blues Deluxe even though these are very different sounding amps.
To me, it shows a lack of understanding of what is actually going on in the tone stack. As a competitor, I'm not going to explain it to Fromel.
The only change I recommend for tone stacks is to change the treble capacitor to a silver mica version. Its cleaner and more articulate.
If you work with a bass player, change C1 to a 2.2uF poly cap. This reduces bass response and reserves power for good midrange.
My secret sauce doesn't involve tone stacks. It makes the Deluxe amps sound better, not just different. Again, maybe someday I'll give away the store. But not yet.


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