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Post subject: Re: Modifications To The Fender Blues Deluxe Reissue Amp
Posted: Mon Feb 22, 2016 10:22 pm
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It appears to me that the mods you describe completely removes the clean volume control from the amp circuit.

Removing R52 and replacing it with a jumper will short out the clean volume control to ground when switched to the clean channel and would be the same as turning the clean volume all the way down. Moving R52 to connect between R9 and the negative end of C36 is the same electrically as the stock circuit connection for R52 so R52 still functions as a load on the output of V-1a. Breaking the trace between R52 and C53, depending on where it was done, would also remove the clean volume control from the circuit. So it appears that the previous owner was too lazy to just press the switch button to select between the clean and drive channel and locked the amp permanently into drive. I don't really understand the value of all this. Are you claiming that the clean channel volume control still functions normally? I don't see how that would be possible.

I never bothered with modding the master volume to work with the clean channel as I prefer the sound of a non-master volume amp (which my other 4 amps are). Given the mods you described earlier, I'm not sure what this mod accomplishes either.

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Post subject: Re: Modifications To The Fender Blues Deluxe Reissue Amp
Posted: Tue Feb 23, 2016 5:10 pm
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"Removing R52 and replacing it with a jumper will short out the clean volume control to ground when switched to the clean channel and would be the same as turning the clean volume all the way down. Moving R52 to connect between R9 and the negative end of C36 is the same electrically as the stock circuit connection for R52 so R52 still functions as a load on the output of V-1a. Breaking the trace between R52 and C53, depending on where it was done, would also remove the clean volume control from the circuit. So it appears that the previous owner was too lazy to just press the switch button to select between the clean and drive channel and locked the amp permanently into drive. I don't really understand the value of all this. Are you claiming that the clean channel volume control still functions normally? I don't see how that would be possible."

This is what is confusing me: Both channels work normally and I don't know why. When on clean channel the volume control worked and the drive and master controls did nothing. When you switched to "drive" the clean volume did nothing and the drive knob and master worked. I'll take some pictures when I get back home (out of town for work until Thursday night). When I saw the mod, I looked at the schematic, scratched my head and said "WTF? This shouldn't work." That's why I pulled the main board out from the chassis to look at it. All I could see out of place I have already mentioned.


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Post subject: Re: Modifications To The Fender Blues Deluxe Reissue Amp
Posted: Tue Feb 23, 2016 5:23 pm
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Duke Sedan wrote:
When on clean channel the volume control worked and the drive and master controls did nothing. When you switched to "drive" the clean volume did nothing and the drive knob and master worked.


That is how the stock amp is supposed to work.

If that is how the amp still works after the mods, then I don't understand the value/purpose of the mods.

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Post subject: Re: Modifications To The Fender Blues Deluxe Reissue Amp
Posted: Tue Feb 23, 2016 11:05 pm
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"That is how the stock amp is supposed to work. If that is how the amp still works after the mods, then I don't understand the value/purpose of the mods."

I am trying to figure out what the hell the PREVIOUS OWNER did before I got into it. My whole point is someone messed with it, it doesn't look like it should still work, but it does. I was wondering if anyone else had knowledge of a mod involving R52 and C53 to give me some insight into what the hell the PREVIOUS OWNER was trying to do and if they modified something else I haven't found yet.

What I did when I had the main board out (TO INSPECT THE CIRCUIT AND FIGURE OUT WHY THE PREVIOUS OWNER HAD MOVED R52, JUMPED R52 ORIGINAL POSITION AND CUT CIRCUIT BETWEEN R52 AND C53), was to jump K2-A and remove R18 in order to have master volume on both channels. This master volume mod had nothing to do with THE PREVIOUS OWNER MOVING R52 AND CUTTING CIRCUIT TO C53.


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Post subject: Re: Modifications To The Fender Blues Deluxe Reissue Amp
Posted: Wed Feb 24, 2016 9:31 am
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Rock Star
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Location: Natural Bridge, Virginia
No need to shout (typing in all caps is considered shouting).

I understand exactly what you are asking. I based my response by tracing out the schematic of the amp. I have found numerous differences between the schematic/board layout drawing and my amp when I was modding it. Fender has been known to make changes to an amp and not back it up with a revised schematic/board layout. Whether the previous owner made the changes or Fender did, I have no idea. The only way to know how the changes really impact the amp would be to see the amp itself. I have no intention of opening up my amp and I can't see yours. Photos may or may not help but would be interesting to see. Bottom line remains, I have no clue why the changes were made and see little value in them.

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Post subject: Re: Modifications To The Fender Blues Deluxe Reissue Amp
Posted: Wed Feb 24, 2016 3:35 pm
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I used CAPS to emphasize certain parts (I see now I could have changed font colour instead). I usually use exclamation points!!! to denote yelling myself, but I see what you mean, so sorry if there was misunderstanding there.

As I said earlier I will take pictures when I get home tomorrow night if you are interested. Also, I wouldn't see the value of this modification even if it was working as one would think it would, but doubly so when the amp still works as originally designed (mind you I don't have an original BDVRI to compare sounds/function to). So I was looking for some other possible reason for moving these components. When I open the amp to take pictures I will check continuity on the associated circuit traces to see if maybe it was a repair done to bypass faulty circuits and look to see if anything else had been moved. And you'll see when I post pictures that you would notice immediately if this mod had been done on your amp and would be extremely disappointed if you found out it was a Fender factory change.

As far as the master volume mod goes, with the master at 12 and the volume used normally I can't hear any difference in sound from the amp as compared to pre-master volume mod. There may be a slight change due to new signal losses/changes but I can't tell. So I see it as the best of both worlds. But it is not useful if you don't want a master volume. I thought the amp was sounding best with the volume around 4 but that was too loud. Now I can set volume at 4 for all occasions. Perfect for my needs (not for everyone though...). I also plan on modifying the reverb circuit to increase reverb signal but most people wouldn't want that either (at least not what I'm planning).

The reverb circuit will be an interesting challenge as I may need to incorporate a tone control just for the reverb circuit. But I'll burn that bridge when I cross it.


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Post subject: Re: Modifications To The Fender Blues Deluxe Reissue Amp
Posted: Wed Feb 24, 2016 4:35 pm
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Rock Star
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Pictures should be interesting.

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Post subject: Re: Modifications To The Fender Blues Deluxe Reissue Amp
Posted: Thu Feb 25, 2016 7:58 pm
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If my images come out OK, you`ll see the scratched circuit board, relocated resistor and jumper where R52 was. If I pull the board again, I`ll try to figure out why it works when it clearly should not.


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Post subject: Re: Modifications To The Fender Blues Deluxe Reissue Amp
Posted: Thu Feb 25, 2016 10:51 pm
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Location: Natural Bridge, Virginia
Guess what?

My amp looks exactly like your amp (I don't have any close ups).

Image

What all this says to me is simple: the PCB and schematic don't match. Most likely the PCB has errors on it which were corrected during assembly. I noticed the mod with the tacked on resistor when I was working on my amp but never really paid attention to it as it wasn't part of my mod work. The spot for R52 is also jumpered in my amp. I don't really see any scratched circuit traces, however.

The bias circuit in my BDRI is the same as the Hot Rod Deluxe III:

Image

and not what the BDRI schematic shows:

Image

The bottom line is: don't trust a Fender schematic to be correct to the amp build.

Mystery solved. Time to go back to playing guitar.

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Post subject: Re: Modifications To The Fender Blues Deluxe Reissue Amp
Posted: Sat Feb 27, 2016 10:33 pm
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Thanks for posting the picture of your amp. Mystery solved for sure. I never would have believed it was a factory line change until I saw yours with the same hack solder job on the relocated resistor. It's funny, the jumper wire looks professionally done, but the resistor solder job looks like a plumber did it (no offense to plumbers meant) not an electrical tech. Next time you are in your amp, if you take a close look at C53 see if you can find a break in the circuit trace. Maybe it's not scratched out as brutally as mine is but it is probably there. I did some continuity checks and the circuit seems to work as the schematic shows.
As an auto mechanic I am used to literal wiring diagrams that show where every wire goes so you can trace problems not just from component to component but also where every wire goes, were every ground is etc... If two circuits don't physically meet at such and such a place it doesn't show it in the schematic, where with amps they show two circuit paths meeting, but they don't meet physically where it is shown. Pain in the $@!.


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Post subject: Re: Modifications To The Fender Blues Deluxe Reissue Amp
Posted: Sat Feb 27, 2016 11:23 pm
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Rock Star
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Glad I could help. Tracing things out on a multilayer PCB can be quite different than tracing a hand wired eyelet or turret board based amp. Enjoy the BDRI. It's a great amp.

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Left to right:

5F1 Champ clone built be me.

Trainwreck Express clone built by me.

Fender Champ 600 reissue modified by me to (more or less) 5F1 spec.

5F6A Bassman clone built by me.

Fender BDRI modified by me and the subject of this thread.

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Post subject: Re: Modifications To The Fender Blues Deluxe Reissue Amp
Posted: Sat Mar 12, 2016 7:12 am
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Hi Bill, I'm newish here. I have a BDRI on the bench and the problem is it has very faint output when drive is selected and the master and drive pots are maxed. Basically not output in drive mode. Red light is on. The + - 16v is good. The 470 5w resistors look brand new. There is some weird residue around K2. I am going to replace the Illinois caps as the 47 and first 22's are leaking electrolyte out the + side, but they still work. F&Ts for replacement.
This is a green board with a date of 2004 on it.
I'm also ordering some new relays. Any ideas?


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Post subject: Re: Modifications To The Fender Blues Deluxe Reissue Amp
Posted: Sat Mar 12, 2016 10:02 am
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Rock Star
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Location: Natural Bridge, Virginia
I'm on my phone right now so I don't have easy access to the schematic.

Definitely replace all leaking caps.

You haven't given a whole lot of other information, so I have some questions.

Does the clean channel work properly? If not, are all the tube filaments lit?

Have you checked all the power supply voltages at both the power supply and each tube? Don't forget heater voltages.

Are all the tubes known to be good? Have you tried swapping the tubes with other known good tubes?

Just because a resister looks good doesn't mean it is good. You should measure it preferably with one end lifted so it is out of the circuit.

Why are you swapping relays? If you hear sound at all in the drive channel it would seem that the relays are good.

That's all I've got until I get home and look at the schematic.

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Post subject: Re: Modifications To The Fender Blues Deluxe Reissue Amp
Posted: Sat Mar 12, 2016 10:51 am
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Yes I've checked all tubes and voltages, checked the vol and drive pots. I assume that because the + - 16V for the op amps is pretty right on that the value of the sand cast 470s is also pretty right on, as well, I have never seen a bad wire wound resistor that doesn't have some physical signs. However I could easily check them. The mute is working during switching. I've done a very thorough physical inspection of this amp and the boards and components, even pulled the main board up to see how it looks underneath. Looks like new. Only thing I found was the electrolyte coming out of the PS caps.
The normal channel is working fine and sounds rather good.
First I'm going to jumper the K2 contacts for the drive mode to confirm that it is working. I'll just tack some temp jumpers underneath.
Why, did I order relays? Because I've read a lot of people have had them fail, so I want them on hand, they are dirt cheap. I might see more of these amps in the future.
I do appreciate the reply. I read through your mod page and seems like most of this amp is pretty cut and dried.
BTW I'm kid of like you in experience, retired AF electronics tech and build my own turret board amps. I don't have an EE though, nor do I presently have much beyond a Fluke DVM .

thank you Bill


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Post subject: Re: Modifications To The Fender Blues Deluxe Reissue Amp
Posted: Sat Mar 12, 2016 11:23 am
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Location: Natural Bridge, Virginia
I'm waiting in my car to pick up my Golden Retriever Lily at the groomers. I'll look at the schematic when I get home and respond further.

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