New Valve Amp - and a great big Fail!

[Skinnyman]

Been fancying a toob amp for a while and the GAS attack finally got the better of me so I ordered a new Fender Bassman 100 from GAK. I looked long and hard at the Ampeg V4B but the intermittent quality issues put me off and steered me towards the Fender

It turned up as promised and all looked good. Tried it out in the spare room and was very pleased with the sound through my Berg CN112s.

I used it on our first gig yesterday and just before the end of the first set, it failed. Lights were on but no output at all.

Fortunately, I'd taken my Genz as a backup so was able to swap over pretty quickly but I'm a bit hacked off that the amp couldn't even make it through a set, let alone a whole gig.

I think the issue is cooling as I've tried it since I got home and it's working now. Obviously, I'll be talking to GAK on Monday (I've bought a load of stuff from them and they're always very good) but while I'm loathe to send it back, I really need something I can rely on.

Has anyone else has similar issues? I've got it on a soak test now to see if I can recreate the fault. I did notice that the input transformer seemed a LOT warmer than the output side so should I be balancing the gain and master better?

Any thoughts before I box it up and send it back?

[dave74200]

Could be a faulty tube. It's nothing you're doing wrong. I don't own a bassman but normally tube amps will switch off when there's a faulty tube. Perhaps one has become loose in transit?

[Billy Apple]

You don't know the horrors it went through in transit to get to yours. A valve may have worked loose. If you've the where with all to do it you could try opening it up and pushing them all down.

But, I'd be looking at returning it

[Skinnyman]

Thanks for the input, guys. I've had the back off and checked the tube seating. All looks okay. I've soak tested it today and can't get the problem to recur. I've even played it at gig volume for a couple of hours (mrs skinnyman was very impressed) and it's behaved faultlessly.

When it failed yesterday,I checked all the bias lights on the back and all we're showing green. The only thing that seems amiss is the fact that the fan doesn't seem to cut in.

So I've emailed GAK to register the issue but I'll try it again at rehearsal and see what happens. I'm loathe to return it as I love the sound. But, equally, it's no use if I can't rely on it.

Could it be a one off caused by the tubes "bedding in"? Or am I just being a naive optimist?

[bumnote]

I have one of these, its fantastic
There is some really good information in the manual on trouble shooting.
I had a very similar problem caused by a faulty valve in position v3 which is a 12AT7

PROBLEM: Signals are present and working normally in the PREAMP
OUT {W} and XLR (PRE position) {AA} jacks -AND- Automatic Bias
display {T} shows all output tubes are good (solid green LEDs), but
the Power amplifier lacks power and punch, sounds different than
normal, or produces no sound from speaker or no signal is present
from XLR (POST position) jack {AA} in ‘SILENT RECORD’ mode.
SOLUTIONS: Power amp driver tube V3 (12AT7) has failed. Replace
V3 with a new tube.

I had to do this after half a dozen gigs and its been fine ever since.

As an aside, Its 40 odd years since I last had a valve amp, it runs to me very hot but fender says this is normal and the fan doesnt cut in untill its almost at nuclear melt down temperature.

[Skinnyman]

That's really helpful, thanks. Dumb follow up question - did you replace one or the set? One of the USPS of the Bassman is supposedly that you don't have to use matched sets of valves?

I'll get some spares and i'll see if it does it again at this week's rehearsal. I didn't check if the pre amp was still working so that's the thing to test.

I really don't want to have to send this back :-)

I notice you have the Neo 410 - happy with it? It's obviously a match for the amp and i'm just wondering whether to get one

[bumnote]

If it is V3 its a single valve and about £10 from Watford valves
the 4 big valves in there are output valves which normally need balancing but the Fender circuit is supposed to balance it
Check the back for the green lights. If they are all in the green the output valves are ok
Try in the the vintage and the modern channels, if no sound praobably the pre amp valves are ok
How long have you had it, I think there is 3 months warranty on valves.
Where are you? Are you able to take it in to Gak, they might have a spare valve to check if that is the problem
I am not a technician, its just what worked for me and I dont want to lead you down the wrong path
VALVE AMPS HAVE BIG VOLTAGES BE CAREFULL IF YOU TAKE THE BACK OFF

[Skinnyman]

[quote name='bumnote' timestamp='1443443282' post='2874675']
If it is V3 its a single valve and about £10 from Watford valves
the 4 big valves in there are output valves which normally need balancing but the Fender circuit is supposed to balance it
Check the back for the green lights. If they are all in the green the output valves are ok
Try in the the vintage and the modern channels, if no sound praobably the pre amp valves are ok
How long have you had it, I think there is 3 months warranty on valves.
Where are you? Are you able to take it in to Gak, they might have a spare valve to check if that is the problem
I am not a technician, its just what worked for me and I dont want to lead you down the wrong path
VALVE AMPS HAVE BIG VOLTAGES BE CAREFULL IF YOU TAKE THE BACK OFF
[/quote]
I spoke to GAK today - really, really helpful. Very apologetic and offered to replace it straight away. However, as it's only happened once and as it worked perfectly yesterday, I've told them I want to try it at rehearsal and a gig this week. If it fails again, they'll swap it, no questions - but if it works, I'll just put it down to a badly seated valve and keep hold of it.

If it does go again, I'll try out the tests bumnote describes and see if I can pin it down.

But it has to be said, I'm very impressed with GAK's service.

[Happy Jack]

Valve amps cab be very sensitive to the mains power supply. I've played in pubs where the mains was so poor (and, frankly, so dangerous) that my rig was receiving well short of 240V.

IME this doesn't just affect power tubes (as you might expect) but also the pre-amp valves in my OTB500. The cut-off point seems to be as the power supply trends down towards 180V. It isn't a gradual or intermittent thing either; the amp works fine until it just stops without warning.

If you use rack gear on stage then you could do a lot worse than to buy http://www.thomann.de/gb/samson_powerbrite_pb10_pro.htm or similar. I have a Phonic PPC9000E in my rack (sadly discontinued) and it was the LED display that first alerted me to the real problem.

None of which will prevent what happened to me at the Ealing Beer Festival last year. The organisers had floodlighting on pylons, only to be switched on at the end of the evening to encourage punters to go home, and to make the clear-up easier for the staff. All the power for the event was being run off a serious diesel generator.

We were halfway through Spirit In The Sky at the end of the set when they fired up the floodlights. The sudden current draw produced a huge dip in supply elsewhere in Walpole Park and my Matamp just stopped dead.

[chriswareham]

Glad that Happy Jack has suggested mains issues, as that was my first thought as well. Had similar problems in certain dodgy venues *cough* Camden Underworld *cough* and it turned out to be fluctuating mains power.

[mrtcat]

[quote name='Happy Jack' timestamp='1443454863' post='2874845']
Valve amps cab be very sensitive to the mains power supply. I've played in pubs where the mains was so poor (and, frankly, so dangerous) that my rig was receiving well short of 240V.

IME this doesn't just affect power tubes (as you might expect) but also the pre-amp valves in my OTB500. The cut-off point seems to be as the power supply trends down towards 180V. It isn't a gradual or intermittent thing either; the amp works fine until it just stops without warning.

If you use rack gear on stage then you could do a lot worse than to buy [url="http://www.thomann.de/gb/samson_powerbrite_pb10_pro.htm"]http://www.thomann.d...te_pb10_pro.htm[/url] or similar. I have a Phonic PPC9000E in my rack (sadly discontinued) and it was the LED display that first alerted me to the real problem.

None of which will prevent what happened to me at the Ealing Beer Festival last year. The organisers had floodlighting on pylons, only to be switched on at the end of the evening to encourage punters to go home, and to make the clear-up easier for the staff. All the power for the event was being run off a serious diesel generator.

We were halfway through Spirit In The Sky at the end of the set when they fired up the floodlights. The sudden current draw produced a huge dip in supply elsewhere in Walpole Park and my Matamp just stopped dead.
[/quote]

Had a very similar issue with an Ampeg SVT2 at a wedding. Cut out just before half time and it turned out that they had caterers making fresh crepes. The huge hot plates they were using got turned on in preparation for the break and the current draw was so bad that my amp just stopped playing the game.