Bright switch issue with Hot Rod Deluxe

[mrr3000gt]

I have a brand new hot rod deluxe III  (yea, I know) and *surprisingly* it has an issue.

It is a few weeks old: and taking it back is not an option...

The issue is that when the bright switch is engaged on the clean channel, the drive channel gain will 'bleed' over to the clean tone channel producing a fizzy forty tone most noticeable when the clean tone channel is turned way down. In fact, when the clean tone channel is turned down to off, any increase in the gain knob makes it audible!

If I disengage the bright switch, then channel switching, volumes, tone stack, and everything works just fine and sounds great.

I do repairs, and have built many amps and the problem does not make sense: the bright switch engages a 0.68uf cap in v2 and is normally disengaged from the drive channel. The channel switch appears to be working fine thruout the circuit.

I have of course checked the 'common' stuff, but it is as if the drive channel bleeds over to the clean channel when the brite switch is switched in...

Aside from reprimanding me on buying one of these notorious repair sink holes, does anyone have some advice and an idea what is going on?

[eleventeen]

"It is a few weeks old: and taking it back is not an option..."

?? Really?

I would suggest googling various word combinations...

hot rod deluxe channel bleed
hot rod deluxe bright switch

and you might get hooked into a more specific forum where someone has had this exact problem. I agree with you, it is hard to imagine how this might happen from a lowly bright switch. I have not serviced many of these, for no particular reason, but then, I am not a tech at a music store where folks would be bringing in amps all the time. But, I have (and it sounds like you have) certainly heard of plenty of goofy situations we tweed/blackfaced dudes are not especially used to, with PC-board construction and ribbon cables running all over.

[mrr3000gt]

I have unfortunately repaired many of these over the years. The newest spin of these amps has 'dual traced' pcb boards and other improvements to address the reliability. From that I can tell, the pcbs look the same to me as the I and II versions.

I also did the obligatory searches to see if I was the lucky person to discover yet another issue these amps have..

I did fix it: it turns out the problem is solder joints, and of all things, crosstalk. Fender it would seem zip ties the V1 shielded connections to the V1 ribbon cable for more than an uncluttered look. Letting the cables move as they do cause LOTS of noise. Zip timing them firmly to the ribbon cable as it was from the factory makes it quiet.

This is 180 degrees from what I learned as an amp builder....

[jjasilli]

??? Is your bright SW issue resolved?

[mrr3000gt]

Yep: the whole still doesn't make total sense to me. There were a bunch of cold solder points on the board and because fender likes to use bendy pcbs on these amps flexing the board makes and breaks connections across the board.
The flexi board and solder points made sense - what did not is that low and no volume on clean channel and any gain dialed in (deactivated in the clean channel) caused the bleed thru of sound and turning the volume knob did not make it go away - all with clicking in a single cap on the cathode of V2....It was when I tied down the V1 connections to the ribbon cable the bleed thru went away...
This I did not like as generally speaking I would think it is not desirable to purposely use crosstalk as a noise cancelation mechanism....

I did look to see what it would take to drop a Hoffman 5f6a board into the chassis and have a nice combo....


Has anyone tried this?

[jjasilli]

I had a similar problem with channel changing SW.  At some point if my HRD fails I may rebuild it with a point to point board.  Dan Torres does as variety of rebuilds:  http://torresengineering.stores.yahoo.net/latmosasform.html

[mrr3000gt]

I just played on it for an hour: sounds great! But i feel like I own a 1975 Harley: looks sharp, runs great but needs constant work to keep it going.

I'll check them boards out: I have built Doug's boards for about 10 years now and have been happy with the results. The HRD has 8 knobs I would like to put to work if I drop in a board.

[joshlam3484]

hi I'm new but I had a question, I recently picked up a hrd used and it seems to me that my bright switch isn't doing anything sound wise I was wondering what would need to be checked so that I could find out what needs to be replaced, the switch seems to work but when turned on I hear no real difference in sound.

[sluckey]

hi I'm new but I had a question, I recently picked up a hrd used and it seems to me that my bright switch isn't doing anything sound wise I was wondering what would need to be checked so that I could find out what needs to be replaced, the switch seems to work but when turned on I hear no real difference in sound.

Looks like you must be in clean mode for the bright switch to do anything.