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Author Topic: Randall Warhead  (Read 3482 times)

p3dsman

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Randall Warhead
« on: June 28, 2014, 11:06:42 AM »
I have a Randall Warhead 1st generation that worked great, but a few months ago I noticed the amp started to lower in volume and "fizzle" out while I was playing. Now, nothing comes out of the speakers period. I have the matching cabs so made sure impedance wasn't the cause.  I have cleaned all jacks and even tried a patch cable on the send/return.

The amp powers on OK, the only way I can use the amp is if I plug the effects loop send into another power amp.

On a side note, the only sound that can be heard is If I turn the volume knobs to max, I can barely "hear" the amp through the speakers, just NO volume whatsoever.

I'm guessing caps or transformer?  It just worked and then fizzled while I was playing one day.

Anyway, I appreciate your time if you have any advice.

J M Fahey

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Re: Randall Warhead
« Reply #1 on: June 28, 2014, 03:33:04 PM »
Plug a known good cable from loop send to return.

Jack1962

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Re: Randall Warhead
« Reply #2 on: June 28, 2014, 04:22:17 PM »
plug into the effects loop send out to a listen amp if you can hear it most of the preamp is working , plug into the effects return with a signal source on the other end and if you have normal output thru your speakers the preamp is your problem. If the preamp test ok then problem is your power amp , the Warhead is a 300 watt amp testing the power amp can be very time consuming.

p3dsman

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Re: Randall Warhead
« Reply #3 on: July 01, 2014, 07:11:13 PM »
Plug a known good cable from loop send to return.

Thanks for the advice, tried it, no luck unfortunately :(  I even cleaned all of the jack inputs very well and checked to make sure contact points were good.

plug into the effects loop send out to a listen amp if you can hear it most of the preamp is working , plug into the effects return with a signal source on the other end and if you have normal output thru your speakers the preamp is your problem. If the preamp test ok then problem is your power amp , the Warhead is a 300 watt amp testing the power amp can be very time consuming.

I have not tried plugging into the return of the effects loop yet, but the send into another amp works 100%; full tone, its all there.  I will do the other side this evening and see if the loop works all the way to rule out the preamp.  If it does end up being the power amp (which I have found something suspicious I will detail below)...I am wondering if it will even be worth it as I will have to take it to a shop.  These are fairly rare, but usually go for ~$600, so not sure the work would be worth it if I can just get another one.

On a side note, I noticed 2 out of the four larger capacitors have a bulge to them on the top of the cap, one in particular is very noticeable.  The circuit board with those on it is small and fairly easy to get out.  If it is the capacitors, as I suspect a bulge on the top is no good, then I can replace those no problem as long as I can find replacements to spec.

I will post some pics later if that would help?

Thanks for all the help, really appreciate it.  :)
« Last Edit: July 01, 2014, 07:13:06 PM by p3dsman »

teemuk

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Re: Randall Warhead
« Reply #4 on: July 02, 2014, 11:12:58 AM »
Quote
I'm guessing caps or transformer? 

Why so? Seems like an automatic assumption for people these days but if the sound simply gradually faded away with slight, fizzy distortion it sounds very much like there is simply an intermittent contact somewhere which gradually got worse and worse up to the point the signal just got muted. So, there may not even be any failed parts in that thing but probably just a solder joint gone bad.

Quote
...the send into another amp works 100%; full tone, its all there.  I will do the other side this evening and see if the loop works all the way to rule out the preamp.

If the send from preamp works fine with another amp then you have ruled out the preamp, at least up to that "FX return" jack.

Quote
On a side note, I noticed 2 out of the four larger capacitors have a bulge to them on the top of the cap, one in particular is very noticeable.  The circuit board with those on it is small and fairly easy to get out.  If it is the capacitors, as I suspect a bulge on the top is no good, then I can replace those no problem as long as I can find replacements to spec.

Bulging could be an indication of an issue, or just result of sloppy manufacturing. Real question is that if you suspect capacitors to be the problem why haven't you taken any measurements to rule them out? If these are, for example, power supply filtering caps have you measured the DC voltage they filter to find out whether that shows any obvious signs of issues...? Just looking at the caps and pondering if they are ok ain't going to answer the question nor fix the amp by itself.

Are you sure you are up to fixing, or trying to fix, this amp? Because quite frankly, you don't seem to be. If issues with a 300W power amp is your first attempt to fix things then may I kindly suggest that the job is likely better to be left for someone who knows what to do to that amp properly. Amateur attempts to fix things can often lead to problems just escalating for the worse.

Quote
it does end up being the power amp (which I have found something suspicious I will detail below)...I am wondering if it will even be worth it as I will have to take it to a shop.  These are fairly rare, but usually go for ~$600, so not sure the work would be worth it if I can just get another one.

You could take it to some shop that repairs these sorts of things, explain the issue and its symptoms, and ask for an estimate of how much they are probably going to charge. They will most likely take a fee for just spending their time to look at it closer and later charge more for additional work and parts needed. So, it's going to be an estimation for the start but hopefully they can give you a ballpark value of what they are probably going to charge, which let's you decide whether it's worth it or not. Possibly you can settle some marginal for expenses after which they should consult you if its still worth it to continue with the repair. Like, if they look at it and find one bad resistor or a solder joint then the work and parts cost likely isn't going to be astronomical in comparison to them looking at it and finding it needs a replacement transformer and a circuit board and is going to cost more than a new, equivalent amp. So, contact some suitable outlet and find out what they can do to it and at what estimated price. They are the only ones who really can tell you this.
« Last Edit: July 02, 2014, 11:26:09 AM by teemuk »

Jack1962

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Re: Randall Warhead
« Reply #5 on: July 03, 2014, 06:20:51 AM »
Any good Amp Shop can tell you exactly what it will cost to repair this amp , it is a very popular amp. Yes they will charge you a bench fee to diagnose the amp , if they don't , don't trust them to do the repair. Now back to the caps , if you can clearly see a bulge in a electrolytic cap it is bad , it needs to be replaced.

TolerBear

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Re: Randall Warhead
« Reply #6 on: July 16, 2016, 10:45:04 PM »
I have a problem with my 2 Warheads in that the effects circuit gives me trouble. Firstly, the effects LED in the footswitch burns out. Then the effects circuit stops working altogether. Does anybody have an idea of what causes that?

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