Blues Deluxe - no sound

[mikell]

Ok, this could be a multiple issue. No sound at all through input jacks. Going through effects loop I have audio but it is very distorted and intermittent (or motor boating) can't quite find the description I'm looking for here. Plan to pop it open in the next day or two but any suggestions on what to look for at first sight? This is my first post here and I haven't yet got the nick for searching yet. This may be an already discussed problem. Thanks, in advance. Oh, this is USA made, mid 90s

Michael

[Enzo]

First, make sure the speaker is plugged into the main speaker jack and NOT the extension speaker jack. It matters.

[mikell]

Good idea. This amp is at a friends house right now. Just picked it up today. I bought this knowing there was a problem. I have a tube tester and some other tubes in storage and wanted to pick them up before I went through it. When I first looked at it I didn't see the jacks but now that I look at the manual and schematics I downloaded tonight I see that they are located under the chassis. That would be funny. I'll check it out tomorrow. I got this thinking it would be a rebuild project all the way but wanted to know if it was salvageable first. I'll let you know.

Thanks for the clue.

[mikell]

Actually, no ext. speaker on this model. Will pop chassis out later today.

Thanks

[52 Bill]

Is there no sound in either mode, clean/distortion?

Before popping out the chassis, check the pre-amp tubes. Check to see if the input jack have been pulled loose from the circuit board.

Try and get it to pass signal first, then fix the sound problems, if any.

[mikell]

Hi Bill, thanks for the reply. The preamp tubes appear okay, unless my ancient tube tester is lying to me. I realize that is a possibility but I think it's working well enough and I'm not showing shorts, etc. While I still haven't removed chassis, I have opened the back. There appears to be some distinct browning in the infamous r 85. 86 area but not at all certain that they are burnt. While I am not able to get any signal through either input wheather on drive or not, I am getting a very distorted intermittent sound through effects return when I plug directly into there. Birthday today, so didn't want to dive deep into it but being that I can't just let it sit there I had to look. These are the first peeks into the amp

[Enzo]

Ah, you have the older version, the newer one has the jacks.

Get out the volt meter. Look at those toasty resistors. SHOuld be about 46v on one end and about 16v on the other end of each. I am betting you are missing one of those voltages. Look at one of the op amp ICs on the board. Is there +/-16VDC on pins 8 and 4?

[52 Bill]

Happy Birthday!

Whatever you do, don't remove the chassis from the amp. You can fix nearly everything on the amp by pulling the circuit board not the chassis.

Check the voltages that Enzo suggested, and also the driver tube and the outputs as well. Injecting a signal into the return jack should deliver a quiet, but otherwise normal signal. You may have a driver plate resisitor issue.

[mikell]

Right you guys are! 46 on one side. Zip on the other. Seems like a good place to start, huh! I'll let you know how it comes out. Hopefully that will be it.

Thanks

[Enzo]

OK. With 46 and zero, that means either that resistor is open, or that the zener it serves is shorted. This is easy to tell. If the zener is shorted the resistor will be REAL hot. if the resistor is open, it will be cold.

[mikell]

That makes sense. However, after pulling the board I have found that the previous owner(s)? or someone did some no-no's. There are 4 places where they soldered wires from end of resistor to a cap or a diode. I guess they thought the traces were bad? Really poor soldering too. If I am going to continue I have to consider repairing this board. There is no telling what this board has suffered. Actually, I pulled one end of these resistors and they are not open. They are, however of the 330 ohm variety. This is beginning to look like a hand-wired bassman or vibrolux or something.

[mikell]

Sorry about that rant. I'm over it now. I guess the color of the burn and the quality of the repair caught me off guard. I will order some parts and work on it again when they come in. I live in a small town and it's either order or travel. Any specific recommendations on cleaning the board? I guess I need to scrape away to expose some copper and repair the tracing. How about wire gauge for the jumpers? . I'm going to complete the Fender recommended changes @ R86 and 87 and will check into R71. Since this is an older amp I am expecting that it is pre updates. Don't know if it matters but although there is no ext. speaker jack there is a main speaker jack. It's not hard wired to the chassis or anything like that. Thanks again

[Functional Dishwasher]

Originally Posted by mikell

Ok, this could be a multiple issue. No sound at all through input jacks. Michael

Michael

I'm a noob, so I may be of no help. I have just purchased a used and abused Blues Deluxe (not a re-issue) and from what I can tell it is dated July 1995. The exterior is really grungy. So today I did the wrong thing and removed the chassis from the case. Didn't know I wasn't supposed to do that. D'Oh! I was just looking to find the QC sticker and check things out. Previous owner said it cuts out at times and everything seemed in good clean visual appearance inside as opposed to the exterior. I put it back together and it works fine. From my guess it hasn't been re-tubed, recapped, or any other mods or rework. Yeah it worked when I got it together. I'm not much for ability to read a schematic and stuff, but I can solder very well. I'm hoping to learn more electronics from this hobby.

If I can shoot a photo of something or check on the voltages or things like that, I've got a DVM and can at least give some clues. Just remind me to unplug the dang thing before I begin to muck around?

Gordy

[mikell]

O.k. guys, you're pretty smart! Got my parts in today, swapped out both resistors to the 470 ohm value (R85 and R86, replaced one zener (CD23)and went ahead and swapped out R71 from 10K to 100K. Boots up and sounds good. Thank you for that. However, as I suspected, there seems to be more afoot.

Drive light comes on and stays on when I turn the unit on, yet I have no drive function, that is, the master and drive pots do not have any effect, no matter what. Both inputs give me sound and one indeed is brighter than the other but that's about it. Also, reverb is not functioning. Any clues?

Thanks, for everything so far,

Michael

[52 Bill]

Originally Posted by mikell

Drive light comes on and stays on when I turn the unit on, yet I have no drive function, that is, the master and drive pots do not have any effect, no matter what.

Does the drive light go on and off with the small pushbutton switch? I've seen the relays fail sometimes, but based on your description, I'd first check to see that the switching voltages are correct. When the drive circuit goes on, one relay should disable the volume control, while the other relay enables the gain and master controls.

Originally Posted by mikell

Also, reverb is not functioning.

First check the small wires inside the tank that connect the rca jacks to the transducer coils. They often break from metal fatigue, but also check where the wires insert into the solderless connectors. Also, check the coils for continuity, you should see somewhere around 160 ohms.

If the tank is ok, there is one chip (U2-TL072) that contains both drive and return functions. Check the voltages at all of the pins. If you get a voltage reading on any pins other than 4 and 8 replace it.

[mikell]

Hi Bill,
Thanks for the reply. No, the button has no effect when pushing. The light is on whenever the amp is on and I can't get it to turn off. As Far as U2 is concerned, I'm reading 16v. on one pin but only about .5v on the other . I am not really showing much of anything on the others. I have just noticed a new wrinkle. My effects loop also seems to be out of commission too. Really, if all I want is a clean loud amp, I have that but of course, I would like to sort this all out. I will pull the reverb unit manana and test but I sure would like to know what's going on with the switching. I don't remember that being an issue before I replaced the resistors and all today. Perhaps I loosened or shorted something? Could a tube be responsible?

Ok, There was one wire broken inside the reverb unit itself that I soldered back on and I see that one of the shields has broken loose on the pc board itself. Its too late tonight to take the board back out but I will reconnect tomorrow, but I tried just touching it to the tiny piece of wire sticking out on this side of the board with no result but we'll see when I reconnect. If that doesn't do it, I will substitue another reverb unit and see what that brings.
Thanks again,
Michael

[52 Bill]

Originally Posted by mikell

As Far as U2 is concerned, I'm reading 16v. on one pin but only about .5v on the other . I am not really showing much of anything on the others.

You should have +16 volts on pin 8 and -16 volts on pin 4 of all of the ICs.

From what I'm reading here, all of your problems still relate to the low voltage power supply, in fact the negative supply to be exact. The FX loop, the reverb and the channel switching all rely on the 16 volt power supplies. If one of the supplies is not working, then all of these sections of the amp will not work correctly.

Because the channel switching bus must go negative to get the clean channel to activate, I think the problem is in the -16 volt circuit. Double check all of the connections and replaced parts and make sure that all of the ICs are getting +and - 16 volts.