Ashdown Fallen Angel 40 DSP

[DeanEVO_Dude]

Ok people, I was mentioned (in another thread) an Ashdown amp that was at a local GC that made no sound, price was just about too good to pass up... $99.00 so I took the plunge (tested the speaker before I put my money down!).

Here is what I've got:
There are no blown fuses inside the amp.
There are no blackened components inside.
There are no loose wires, cut wires, or burned wires.
It powers on and does not blow any fuses at all.
I plugged a cable from the "effects send" jack into another amp and I got sound, not dry, crackly, distorted sound, it seems good solid sound out the preamp. DSP works, as well (effects sound like crap, but it works).
I get nothing from the power section, not even a "snap" "crackle" or "pop" from the speaker when I flip the standby switch to the on position.
Inside, the preamp and the power amps circuits are on two seperate boards, seems like a very effective way to build a circuit-board amp.

Anyway, my question: Where do I go from here? and how do I procede to check the power amp section to trace signal/voltage to find out where my problem might be? Also, what is the best way to check the Output trans? I am hoping that this is a fairly easy repair, but I've got to diagnose the exact problem(s), since I don't have a huge "chunk of change" to throw at it. If I can keep the repairs down to $100 to $150 max, I got a great amp at a great price.

The tools I have at my disposal are DDMs, soldering iron and hand tools, I do not have access to a scope or signal generator.

Thanks all, cheers!

[tunghaichuan]

Ok people, I was mentioned (in another thread) an Ashdown amp that was at a local GC that made no sound, price was just about too good to pass up... $99.00 so I took the plunge (tested the speaker before I put my money down!).

Here is what I've got:
There are no blown fuses inside the amp.
There are no blackened components inside.
There are no loose wires, cut wires, or burned wires.
It powers on and does not blow any fuses at all.
I plugged a cable from the "effects send" jack into another amp and I got sound, not dry, crackly, distorted sound, it seems good solid sound out the preamp. DSP works, as well (effects sound like crap, but it works).
I get nothing from the power section, not even a "snap" "crackle" or "pop" from the speaker when I flip the standby switch to the on position.
Inside, the preamp and the power amps circuits are on two seperate boards, seems like a very effective way to build a circuit-board amp.

Anyway, my question: Where do I go from here? and how do I procede to check the power amp section to trace signal/voltage to find out where my problem might be? Also, what is the best way to check the Output trans? I am hoping that this is a fairly easy repair, but I've got to diagnose the exact problem(s), since I don't have a huge "chunk of change" to throw at it. If I can keep the repairs down to $100 to $150 max, I got a great amp at a great price.

The tools I have at my disposal are DDMs, soldering iron and hand tools, I do not have access to a scope or signal generator.

Thanks all, cheers!

The first thing I would do is read up on working on tube amps safely, a 40W amp stores enough energy to kill you, or shock you very badly. So be careful.

See if Ashdown will give you the schematic:

http://www.ashdownmusic.com/tech/schematics.asp

To test the OT you'll need a small AC wall wart, 6VAC to 12VAC works nicely. This page explains the impedance and turns ratio:

http://www.radioremembered.org/outimp.htm

You'll need to make sure no tubes are plugged into the sockets an the speaker is not plugged into the output jack.

This site gives you the rundown on how to check your OT:

http://www.geofex.com/ampdbug/outtrans.htm

One thing you might want to check is to make sure the screen grid resistors connected to the power tubes are the proper values as stated on the schematic.

Without a signal generator or a scope, it will be hard to diagnose the problem if it isn't a simple fix.

Finally, you may want to check with these guys:

http://music-electronics-forum.com/

There are lots of techs there with decades of experience.

Good luck with your project, I hope you get it working quickly and easily.

[DeanEVO_Dude]

Ok, excellent stuff. I think that I could come up with a low-voltage, ac wall-wart. Based on the fact that it does not blow fuses, would it be a fair deduction that the OT is either ok or open on the primary or secondary?

Thanks.

[tunghaichuan]

Ok, excellent stuff. I think that I could come up with a low-voltage, ac wall-wart. Based on the fact that it does not blow fuses, would it be a fair deduction that the OT is either ok or open on the primary or secondary?


I can't say for sure. One thing you might want to do (if you haven't already) is to check the fuses with your DMM to make sure that they are not blown. Sometimes a blown fuse looks just like one that isn't.

What tubes does the amp use, BTW?

[DeanEVO_Dude]

I can't say for sure. One thing you might want to do (if you haven't already) is to check the fuses with your DMM to make sure that they are not blown. Sometimes a blown fuse looks just like one that isn't.

What tubes does the amp use, BTW?

That was the primary purpose for opening it up... Checked all the fuses, with my meter, none blown (good and bad, I suppose).

It has 4 12AX7s and 4 EL84s. I don't have any spare tubes to swap, but I do have an amp that I can try the tubes in to see if they are good. If I test them, one at a time and they work, does that mean they will work in pairs as well?

[tunghaichuan]

It has 4 12AX7s and 4 EL84s. I don't have any spare tubes to swap, but I do have an amp that I can try the tubes in to see if they are good. If I test them, one at a time and they work, does that mean they will work in pairs as well?

They should. A working known-to-be-good amplifier is the best kind of tube tester.

What amp will you be testing the EL84s in?

[DeanEVO_Dude]

They should. A working known-to-be-good amplifier is the best kind of tube tester.

What amp will you be testing the EL84s in?

My little, slightly modded Crate V5... Yeah, I know it will be a pain, just gonna have to take the chassis out of the cab to test them.

[DeanEVO_Dude]

Well, when work does not keep me too busy, I can get some time with my new GAS project. So, I tested all 4 tubes, "brand new" acording to the folks at GC where I bought the amp. They all worked flawlessly in my V5. The next step is to test the OT and see if it is open, and to check the wires from the preamp board to the power amp board and to the output jacks, etc.

As for the tubes, they are all Groove Tubes GT-EL84S tubes, and they all have a number on them, 2 of them have a "7" and 2 of them have a "5" on them. When I get the amp working, should I put them with the sevens on one side and the fives on the other? or should I put the matching pairs middle two and outter two? Just curious, since it might be a little while, depending on how much I spend to repair the amp, before I can get a matched quartet.

I also sent off a request for access to the Ashdown technical section of ther site.

Cheers.

[DeanEVO_Dude]

Well, I got the schematics emailed to me last night by Guy at Ashdown. Excellent customer support, by the way. Started looking at them to figure out a "plan of attack" for today, after I got off work... Marked some things to check, some places to look for signal, etc. Got off work early enough to pull the amp apart agin, got out the flash light so that I could take a closer, well lit look at the board befor I started sticking my meter in there with it on... Stupid, blind, duhhhhh me!!! I missed a fuse! "Hidden" under the bent chasis, on the edge of the circuit board. Well, wouldn't you know it, blown, bigger than s**t! 500ma, 350v, drove down to the local Shack, looked... No 350v fuses! So I got a 500ma, 250v, slow-blow pack of fuses and hoped all the way home that they would work. IT DID! I now have a working amp, for $100 plus the cost of a fuse. I have often wondered what it was like to be on the recieving end of one of those "killer, in the right place" deals! Now I know... LOL

P.S. I do feel really stupid though...

Thanks to all who replied here to offer links and suggestion. Cheers all!

[tunghaichuan]

As for the tubes, they are all Groove Tubes GT-EL84S tubes, and they all have a number on them, 2 of them have a "7" and 2 of them have a "5" on them. When I get the amp working, should I put them with the sevens on one side and the fives on the other? or should I put the matching pairs middle two and outter two? Just curious, since it might be a little while, depending on how much I spend to repair the amp, before I can get a matched quartet.


I'd put one matching pair as the outside tube and the other matching pair as the center pair: 7,5,5,7 or 5,7,7,5.

[tunghaichuan]

Congrats on the score. Luckily it was something very simple. Keep an eye on it though, fuses blow for a reason. Not trying to be a downer, you good a great deal on the amp.


Well, I got the schematics emailed to me last night by Guy at Ashdown. Excellent customer support, by the way. Started looking at them to figure out a "plan of attack" for today, after I got off work... Marked some things to check, some places to look for signal, etc. Got off work early enough to pull the amp apart agin, got out the flash light so that I could take a closer, well lit look at the board befor I started sticking my meter in there with it on... Stupid, blind, duhhhhh me!!! I missed a fuse! "Hidden" under the bent chasis, on the edge of the circuit board. Well, wouldn't you know it, blown, bigger than s**t! 500ma, 350v, drove down to the local Shack, looked... No 350v fuses! So I got a 500ma, 250v, slow-blow pack of fuses and hoped all the way home that they would work. IT DID! I now have a working amp, for $100 plus the cost of a fuse. I have often wondered what it was like to be on the recieving end of one of those "killer, in the right place" deals! Now I know... LOL

P.S. I do feel really stupid though...

Thanks to all who replied here to offer links and suggestion. Cheers all!

[DeanEVO_Dude]

Congrats on the score. Luckily it was something very simple. Keep an eye on it though, fuses blow for a reason. Not trying to be a downer, you good a great deal on the amp.

Thanks! No problem. Acording to tech supt., that fuse blows quite readilly when a power tube goes bad. Since the nice folks at GC changed all the tubes... :applause They said that they could not go any lower on the price due to having around $300 into the amp... Good thing that they don't have an amp tech on site there! :poke

Now, if I can only get rid of alot of the excessive bass on the drive channel... :happy