Roland AP7 Jet Phaser not phasing

[mindwave_21]

Hey all!  Long time no see.  I've been out of the loop for a while, but I've gotten the bug again during winter break!  Hehe...

Ok, so I've got this old Roland AP7 Jet Phaser from a friend, and it's not working fully.  At first, it was just bypassing, but I found out that the batteries haven't been changed since 1999 (hehe...hardwire bypass I guess).  So I changed out the batteries and voila, the fuzz and distortion work...albeit very quietly.  It's about half as loud when engaged compared to the bypass.  Also, the phase doesn't work at all in any of the distortion, so I just get "pure" fuzz and distortion.  When I turn it to the clean phase modes, I get just a quieter sounding clean signal with no phase whatsoever.  I took a look at the insides and the wires seem to all be in place...so I don't know where to start.

Sorry, but I've only built 2 pedals and they went off without a hitch.  No I have a marketed pedal that doesn't fully work, and I don't know what to do!  I'm thinking about changing out the IC's, but I don't know which ones.  Any other places to check?  How do I check?  Here's a bunch of pictures of an identical pedal to mine:
http://www.modezero.com/jet_phaser.htm

Any and all help will be appreciated, thanks!

PS - How hard is it to make this pedal true bypass?  If I'm going to be messing around with the insides, I figure I'd make the effect work first and then switch it out for true bypass (or is it true bypass already with the DPDT?).

Thanks again!

[Johnny Guitar]

I've had my Jet Phaser go down three times in the almost thirty years I've had it. The first time I took it to a shop -- ouch! I can't remember what the problem was or what the repair involved. All I remember was it was painful to sit down for a week  :shock:  :wink: .

Both the other times I've fixed it I found there was one bad IC. The only thing I really remember about both my later (home) repairs was that the LFO stopped working -- there was no discernible phasing sound.

The second time it went down I remember having trouble finding what the IC was (20 years ago -- no Google) and ended up replacing it with an LM 324 and it worked fine.

The third time it went down (same symptoms as I said) I went straight to the LM 324 and that solved it.

However, I don't remember having a gain problem on the output level in "Jet" mode. but I think finding the LFO IC and replacing it with a 324 will get you started.

But the best thing you can do before you get started is build the "audio probe" which is refered to so much around here. I just built mine this past weekend -- but the number of times I was doing something and thought, "I wish I had some way of hearing what is going on in this bloody...." -- really it's well worth the twenty minurtes (or less) it might take you.

Good luck!
John B.

[mindwave_21]

Thanks Johnny, I'm going to Fry's to see if they have those.  I think the stock LM2902 and LM324 are interchangeable, but rither one of them is definitely ok to use from what I've read at this site.  Which one is the LFO Op-amp?  I have no schematic, and I'm relatively new at building (actually, only built a compressor and distortion, never an oscillator), so sorry for the question.  Do I replace all 3 op-amps?

Thanks again!

[mindwave_21]

Hey all
Just got back from Fry's and couldn't find the LM2902 or LM324, because they only sell NTE electronics parts.  I did a cross reference search online and got the NTE987 as an alternative quad amp...anybody had experience with this IC?  I know it says it's a replacement, but will it do the phaser justice if I put 3 of these in it instead of the LM324 or LM2902?  Why can't there just be a universal name for these darned things...

Edit:  here's a spec sheet if you're interested
NTE987
http://www.nteinc.com/specs/900to999/NTE987.html

[Rodgre]

When I got my Jet Phaser, it had been sitting for twenty years probably. It didn't work.

I cleaned the pots and switches with tuner cleaner, or Deoxit...something like and and she works like a charm now.

Don't always assume something drastic is wrong!

Roger

[mindwave_21]

Am I de-soldering or disassembling any pots here?  Or can I just spray deoxit on the pots directly while they're wired up?  I'm going to have to go to the store to get some anyways (don't even know if they have it...what are alternatives?), so I'll just throw down 5 bucks for some IC sockets and 3 NTE987's and goof around to see if I can put the LM2902N's that work where they're critically needed (after cleaning the pots and checking of course).

EDIT:  BTW, what does the trimpot on the circuit board adjust for?

[puretube]

send or PM me your e-mail address (forum@puretube.de)...

[Rodgre]

As far as cleaning the pots and switches, no disassembling. Just spray tuner cleaner or some other electronic cleaner/lubricant into the pots and switches and crank them around a bit to get them lubed up.

That's what fixed mine, anyway.

Roger

[mindwave_21]

Ok, so here's an update:
I took out the old IC's and replaced them with sockets so I could interchange chips if I have to.  I installed 2 TI LM324N's and an NTE987 (which are suppossed to be equivalents to the stock chips), and I'm getting the same problem:  No oscillations to speak of, but good fuzz and distortion.  I also noticed that I had to wiggle the instrument in jack to get it to play, so I looked at those connections and they seem to be alright.  Anymore suggestions on how to fix this?

PS - I used a non-oil contact cleaner for electronics (just alcohol mainly) to clean the pots and switches, but still nothing.

[lion]

I have a non working AP7 laying around I'd love to repair. The (first and hopefully the only) problem is that most of the wiring, for some reason, is disconneted - and I can't figure out what is going where, and if anything is missing.
Can someone help me with a schem - some guidance on wiring details, or maybe some close up pics of the wiring?

Erik

[puretube]

send or PM me your e-mail address (forum@puretube.de)...

[mindwave_21]

So I guess dr said there might be a FET somewhere causing all the trouble.  How do I check these transistors and where are they (dr or puretube, anybody)?  Also, they're 2SK30A-Y, and I don't have a clue if they stock those at my local hardware store.  I read somewhere a J201 put in 180 degrees from the pin layout would work, but I'm not quite sure.  
I thought vintage effects that used to work were easier to debug than homebrew circuits...sheesh...

[mindwave_21]

Ok, sorry to keep this post alive, but my issues aren't resolved yet and I'm still looking for help.  Thanks to the help and advice of dr and puretube, I FINALLY built an AUDIO PROBE (yay...been wanting to do that for some time now...damn I'm lazy  :lol: ).  I've also tried freezing FET's one at a time with some upside-down air duster gas to see if I could kick-start them.

So here's where I'm at now.  
1. Replaced IC's
2. checked for some bad solder joints/wires
3. Froze FET's
4. Checked diodes for reverse bias integrity

I tried using the audio probe and a CD player as effect input, and got sporadic results at best; certain components made sounds, usually the song on the cd player or lots of loud clicks from certain IC sockets (some sort of calculation output or something?), many others were dead quiet.  Tried the FET's and got signal from a few, no signal from the others.

So here's what I'm thinking.  Either I missed a bad solder joint, one of the FET's is dead, or one of the electrolytic caps are dead.  In addition, I forgot to mention there's a 6-way rotary switch on the box, and I've only tried 2 out of 6.  However, the results in each setting were pretty much identical, so I'm assuming that that's not really an issue (the thing is supposed to distort and phase at the same time, so I think a majority of the cirduit is supposed to work).

Can someone enlighten me on how to use the audio probe methodically to find bad components.  I'm thinking that I follow the circuit like a maze from the input until I come across something with no signal (although I think the ground trace is supposed to be silent, no?).  Problem is, I'm not sure where the input starts from...

I'm also thinking of just going to Ratshack and throwing down the heinous $5-10 charge for about 6 electrolytic caps that are on the circuit.  Any suggestions before I go out and blow some money?

BTW - On the schem, it asks for a 1uF NP/50V cap, and I have a 1uF film cap that reads " 105 S 5N".  Is that sufficient as an equivalent?  I remember reading somewhere that film caps have very high breakdown voltages when compared to electrolytics.

Thanks for all the help!

EDIT 1/11/05
Found some bum JFETS, but not sure if they're 2SK30AY or 2SK30A-Y, but NTE's cross listing gives different results for the 2 numbers...