Vox Pathfinder 15 Doesn't seem quite right.

[Commodore 64***]

So, I picked up a Pathfinder 15 from Craig's List today. It's an older one, with no reverb. Off the bat:

1. Tremolo doesn't work.
2. Does not seem very loud. With the volume dimed, Gain at about 9-Oclock (1/4 turn), the volume is very low. Like barely audible. I was sitting next to it on a bed playing, with the volume dimed and the gain at 12-Oclock, and it wasn't even close to being too loud.
3. The speaker farts out horrificly. It really sounds like ***. Even at these low volumes, the E and A string open cause it to fart out. Sounds nasty.

The amp can't be this bad can it? There has to be something wrong, right? I have loads of capacitors and resistors and a soldering iron. Someone help me get started troubleshooting.

[sumitomo]

Well after soldering and testing don't work,break out the 5 lbs. precision adjusted and go to town!!! Sumi

[ZMAN]

I have the 15R and it is plenty loud. Mine is new and was impressed with how good it sounded. There must be something wrong and I am sorry I can't help with the electronics. If it doesn't work I take it to the shop. I can fix just about anything mechanical but electricity scares me!

[Eric***]

My main guess, which is no better than yours, is that either something is loose or maybe they put in a new speaker that's ridiculously high resistance, like a 16-ohm or something (I think that would suck power out). That's the limit of my electronics expertise.

Do you have a multimeter? That would be your best tool in troubleshooting.

[Commodore 64***]

http://aga.rru.com/TechTips/disp.cgi...t/voxc30ldr.tt

by Robert M. Braught

As some of you techs know by now, the tremolo 'assembly' (opto-coupler p/n LT9914) has a reputation for failure... causing distortion in clean channel operation, poor/no tremolo... one on the frizz can make the amp sound like the output IC's blown...

Word from Korg USA last week, no 'recall' in the near future, no substitute part recommended, etc. From my field experience it appears the LDR portion fails, possibly linked to voltage/current (? customers have reported after 'blasting' signal through their amp, it 'quit'.) List price on the 'original' Vox(Korg USA) part $24

I've successfully tested a 'regular' Vactrol, ala Fender p/n 16282, OEM # VTL5C3/2 as a suitable replacement. Use both LDR elements in series (leave the center wire unconnected / clipped.) The circuit will require 'recalibration', twiddle ref VR11 and VR12 (on the main board) 'til tremolo sounds right ('normal' full depth) and signal pass is good with tremolo 'off'. No harm will come from the adjustments being dimed or turned back full CCW. This sub is less than half the part cost of the orig Vox part, and my experience with the Vactrol units (as in Fenders, etc) is that they are a very high reliability part, with long life expectancy. FWIW this will not change your tone.

Probably can't use something designed for a 30w in my 15w, though huh? But there does seem to be hope. Just gotta find the right part.

[Spudman***]

Sounds like a connection of some kind. Either a lose wire or bad solder connection. Have you tried new tubes?

If you are getting any signal I would take that as a good sign. Probably your issue can easily be fixed.

[M29]

Can you try an extension speaker?

I would think it is a bad connection somewhere too. If it has a power fuse try a new one.
Try wiggling wires while it is on and see if you get any reaction like static or volume change. Wiggle the cord at the input jack, speaker wire.

Just a few things off the top of my head.

[Commodore 64***]

I really don't think it's a connector or speaker problem It sounds a lot like the optocoupler problem on Cambridge series (this old pathfinder is probably same time period). There's a .rar file on this site that has a ton of info. : http://www.cruses.se/cam/index.htm.

Here's a little taste:

Vox Cambridge 30 Modifications from Harmony Central

The following comments were lifted from a Harmony Central review for the
Vox Cambridge 30 Twin Reverb.


FOR ALL C30 OWNERS!!!!! READ THIS!!!!!!! THIS IS VITAL !!!

The villain of all bad reviews of this amp has a name and location!! It is a crap part that was used on the amp!

It's the opto-coupler model LT9914 which is responsible for the tremolo and its located on the circuit board next to the volume pot, all users MUST change this part for a VTC5L3 optocoupler!! even those who didn't yet have the problem.

All you hear about crappy sound, low volume, volume variation while playing (after getting warm).....

Found a replacement part: http://www.alliedelec.com/search/pro...px?SKU=9800710

[Eric***]

So...it's that optocoupler, but the guy was also talking about a couple of pots and an opamp? That was a little rough to follow. Probably didn't help you that he got the model of the replacement optocoupler wrong too.

Anyway, that's good that you have a probable culprit.

[Commodore 64***]

So...it's that optocoupler, but the guy was also talking about a couple of pots and an opamp? That was a little rough to follow. Probably didn't help you that he got the model of the replacement optocoupler wrong too.

Anyway, that's good that you have a probable culprit.

I ended up getting in email contact with a guy. He rebuilds Cambridge amps. That chip stuff related to Cambridge amps, it doesn't apply to my Pathfinder, so I removed it, heh.

But yeah the actual part is a VTL5C3 .

[Kazz]

Dude......did you buy this without testing it? I would think after your last Craigslist blooper that you would have insisted on testing it out before shelling out the cash.

[Commodore 64***]

Dude......did you buy this without testing it? I would think after your last Craigslist blooper that you would have insisted on testing it out before shelling out the cash.

I bought it as-is for a good price. It's 50 dollars, not 500. I have no issue with the seller or the purchase. I just want to know how to fix it. And it looks like it's likely to be $4.50 part.

[Commodore 64***]

Just got a schematic from a person, with whom I've dealt with on CL. I wish he'd make an account here, he knows a ton. In any case, he added reverb to a Epiphone Valve Jr., and I was thinking of maybe trying something similar with this Vox (as long as I have it apart), using a Belton module. Just gotta figure out where to get 5v from the Pathfinder.

[Duffy]

The Vox Pathfinder 15R is an awesome amp, very loud 15 ss watts, great tone and variability with a great reverb and tremolo, hallmarks of this classic amp, reminicent of the AC15 and AC30 style, but inexpensive and ss.

Your amp has serious problems, problems that you probably are not capable of diagnosing and fixing, certainly by touch and go methods.

I would take it to a qualified tech and have it checked to see if it is worth fixing. Many things could be wrong. More than one thing could be wrong. The tremolo should work for one and it should be loud. There are two standout problems right off the bat.

A new Pathfinder 15R costs 139 dollars and has a warranty, and should last over twenty years of trouble free play, with no problem.

Maybe someone tried to jack this one up to use in a heavy metal band and overamped the thing to the point of ridiculousness. It could just be blown out, blown out transformer or such and could be expensive to get looked at and fixed.

I hope you can get it checked out by someone without incurring too much cost and then make a decision if you want to work on it.

I have a Vox DA5 also, that is an awesome "Chromie" with modelling and effects and works off "C" cell batteries or wall current. It is great for taking camping and has a switch to switch down to a half watt, two watts or five watts. It is loud a a half watt and will play for six hours on a half watt. Great for camping trips.

[DeanEVO_Dude]

I don't know if I missed it or what, have you another speaker to try? It does sound like you might have a blown one.
As for the power rating of the speaker, it should not matter too much. If you have a 15 watt amp and put a 25 watt speaker in there, there should not be much volume loss at all. What you get with the hight wattage speaker is less or no speaker break-up. What will give you a volume change are the other two speaker specs; Sensitivity and Impedance. Lower impedance could/will cause damage to the amp and louder (precieved) volume, and higher could/will do the same. Lower sensitivity will have a lower volume and a higher sensitivity with be louder. I have a 30 watt amp that has a 75 watt speaker in it, it is not any louder than the one it came with originally, but it does not break-up at cranked volumes like the OEM did.

So, bottom line? I would try a different speaker before the 10lb adjustor. Hope this helps a bit. Cheers!

[Commodore 64***]

My Allied order came today. Replaced the optocoupler, and the Vox Pathfinder rides again. All better now. I can't say for sure yet, but I think I might like the Vox tone better than my SF Champ (*gasp*).

Very simple, unsolder 4 leads remove bad part, put in new part and solder back on 4 leads.

Should anyone else stumble across this thread whilst troubleshooting or googling "Cambridgitis", shoot me a message, I ordered 3 extra optocouplers, and it won't cost much for me to drop one in a regular old envelope (they are very small).

[DeanEVO_Dude]

Good job! Great to hear that you got your new (to you) amph workin' again! Gotta love them easy fixes, huh!

Cheers!

[kerc]

Pathfinders are great little amps. I played mine constantly since 1998 until the tremolo went this year, and then it started sounding like crap.

I still have it there, wishing it'll come back from the ashes like the phoenix.

Sigh.

[Commodore 64***]

Pathfinders are great little amps. I played mine constantly since 1998 until the tremolo went this year, and then it started sounding like crap.

I still have it there, wishing it'll come back from the ashes like the phoenix.

Sigh.

ONe of the symptoms of optocoupler failure is the trem....