Clean channel Hot Rod Deluxe

[M Fowler]

Anyone build this? I would like to build an amp to bolt in the HRD combo cabinet.

Two of my friends love the Hot Rod Deluxe because they say it has sparkle and loads of head room but the amps are plagued with breakdowns.

Latest episode is channel switching went out.

I looked at the schematic and eliminated the relay switching for gain channel and reverb as well in my drawing and no I can't figure out how to use the schematic drawing tools.

Does this look right?

They want clean channel only, lots of headroom and run pedal board in from front.

Mark

[ampdoc1]

You are gonna have your hands full with a rewire. Most of the circuitry is on the bottom of that shitty PCB. In my experience with that and the Blues Deluxe/Deville, the transistors/FETs (Q1-4) controlling the switching functions are almost always the culprits.

[gingertube]

I think there might be a problem with your traced circuit at the grid of V2A (pin 2). Are you sure that the 1M and the 250pF are in series to 0V?

Also you said that you only wanted the clean channel. Four gain stages is not going to give you clean.
I think that the relay switching you eliminated probably switches the clean signal around 2 of those stages.

Can you provide a link to the original schematic so we can check?

Cheers,
Ian

Edit:
OK I found the original.

You did a reasonable job with a few mistakes.

The bright switch on the cathode of V1B goes to 0V direct, not via the 1M. In the original that connection to 0V is via a relay contact which prevents the bright switch having any function when DRIVE is selected.

Similarly there is a relay contact from the 250pF/1M join at the input to V2A which connects the bottom of the 250pF to 0V when DRIVE is selected (to cut some highs). For clean ONLY delete both the 250pF and 1M.

Next V2B and the Master control are bypassed in CLEAN (DRIVE OFF) with the output taken from the anode of V2A

There is a MORE DRIVE signal which appears to switch in a 1uF cathode bypass cap on V2A and a 25uF cathode bypass cap on V2B. V2B is out of circuit for CLEAN and I think that the 1uF for V1B is also out of circuit for CLEAN.

I'm fairly sure that the 250K Volume pot is a linear and it relies on that 100K from the wiper to 0V to give it a fake LOG response.

Hope all this helps. (I see that there have been other responses while I have been busy editing).

Cheers,
Ian

[M Fowler]

HRD schematic

[renshen1957]

Anyone build this? I would like to build an amp to bolt in the HRD combo cabinet.

Two of my friends love the Hot Rod Deluxe because they say it has sparkle and loads of head room but the amps are plagued with breakdowns.

Latest episode is channel switching went out.

I looked at the schematic and eliminated the relay switching for gain channel and reverb as well in my drawing and no I can't figure out how to use the schematic drawing tools.

Does this look right?

They want clean channel only, lots of headroom and run pedal board in from front.

Mark

Hi,

After my experience with Fender PCBs, my recommendation:

Gut the Amp;

Keep the Iron;

Dispose of the PCB;

Rebuild the circuit on either eyelet circuit cards, turrets, or point to point terminal strips. Or build something new/better, with better parts.

It will take less time, grief, and frustration on your part.

Fender has barely adequate components, thin copper traces, basically the Hot Rod series was fine for the occasional weekend, day job player, but after 3 to 5 years of heavy duty professional work, the heat starts to life the PCB traces and they're toast.

The mid 1950s Tweed Pro in the family is still going strong 57 years later.

Best Regards,

Steve

[gingertube]

See edits above.
Cheers,
Ian

[M Fowler]

Thanks for the responses guys and I do plan to either make a new chassis or gut the old chassis.

Ian, thanks for your help I really appreciate your efforts and I changed my schematic on V1B and V2A but still wondering about V2B being in the circuit.

I have been looking at the Fender Bassman 6G6 circuit which is similar, no?

Mark

[gingertube]

Mark,
Look at relay K2A in the original circuit. The relay is switched by the DRIVE control and is shown in its un-energized state (that is DRIVE OFF or CLEAN). The signal is taken from V2A anode, V2B is bypassed.

NOTE: Any professionally prepared schematic will always show their relays in the un-energized (OFF) state.

The Fender 6G6 circuit looks superficially a little similar but is very different and is likely to sound very different too.

The HRD Clean is this structure:
Gain Stage => Volume => Gain Stage => FVM Tone Stack => Gain Stage => power amp

The 6G6 is a this structure:
Gain Stage => Cathode Follower => Bass Control => Volume Control => Gain Stage => Gain Stage => Treble Control => Power Amp

Cheers,
Ian

[M Fowler]

Ian thanks I will study it a lot more.

[Drew.12345]

Mark,

If you make any progress on this project I would like an update
I have a HRD that I just use as an extension cab cause my pcb crapped out on me and I got tired of adding jumpers and replacing resistors.

I have been thinking of just gutting it and using the iron for a JCM 800 2204.

I did like the headroom and clean of the hrd but way too unreliable to count on.
On the bright side, this amp did teach me many things about tube amp repair though.

Drew

[M Fowler]

Drew I have not done anything further other then go over the schematic more dropping off the V2B gain because we only want clean channel.

From my google experience most guys are just gutting the HRD and putting in old Fender circuits as replacement but I'm with you I like Marshalls.

I think I'll get Ddawg to build me a replacement blank chassis and build the amp based on the values of the HRD without any dirt or distortion gain stages, clean only. But I'm not going to rush into this build. If there are that many HRD amps sitting idle around the USA maybe I can give some life to them with a replacement chassis

Mark

[stelligan]

PM groovetubin. He has been all over this Fender I think.


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