I've finally settled on an amp after some labouring and actually bought back an Egnater Rebel 30 Mkii. It takes pedals really well, although I'm not touching the second channel. It hasn't been revalved and it makes sense to have backups so I'm looking to replace the stock ones and keep them as spares.
This is a recommended package (which is look to get from the UK):
http://www.thetubestore.com/Shop-by-Amp/Egnater-Rebel-30-Amp/Egnater-Rebel-30-Premium-PackageAnybody any thoughts on it?
Also, I have a multimeter and have already pulled the amp out of the head for a look. Ideally I'd like to re-bias it myself, while avoiding death.
There's a schematic here:
http://www.rig-talk.com/forum/download/file.php?id=14221And this is apparently what needs done:
There are two trim pots and 3 test points. The bias voltage is printed on the circuit board (40mV +/- 4mV) and you measure between TP1 and TP2 and then TP2 and TP3 while adjusting the appropriate trim pot. It is printed on the PCB which test points to use for each trim pot. Re test after 5 mins and you're done.
I've identified these bits. Plug in a speaker when doing it, yes? Safety advice or simply go to an expert?
Comments
Yes, you need a speaker connected really - just for the unlikely event that the amp is unstable with no load. Or you could use a deliberately shorted plug in the speaker jack if you prefer, that's completely safe for the amp.
Keep your hands off the amp while it's on - place or support the chassis so it can't wobble or fall over. Most important of all, never hold the chassis with one hand while poking around with the other, even with a tool. If you slip and touch something live the current will then travel up one arm, across your chest and down the other, which is the most likely to kill you. If you simply touch something live when the current doesn't have anywhere else to go at the other end, it will hurt but it's unlikely to do any real harm - this is why you will sometimes see old-school techs working with one hand in their pockets, just as a precaution. But if you're sensible you won't be touching anything live anyway.
I think that's about it, other than don't get distracted or allow yourself to be surprised by something, that's when accidents tend to happen.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
All good advice. How much do you need to turn a trim point usually? Fractional adjustments, I imagine?
My band, Red For Dissent
Usually - if the bias circuit is well-designed - the trimmer isn't too 'touchy', but some are...
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
My band, Red For Dissent
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
Just thought it was worth a mention.
I think I might get somebody to show me the biasing. Being dead might be crap.
My band, Red For Dissent
To amplify (Boom! Boom!) ICBM's point about 'distraction'. No kids, no animals and stone, cold, sober.
Ideally you should have another 'responsible' adult within earshot.
I like to tell peeps to use croc leads to connect into the circuit, can be done cold, then power up and tweak. I see there are two bias points and so that is bit more of a faff. I cannot find an actual schematic but I assume there is a test point and setting for each OP valve and so getting the readings the same value is more important than getting the Absolute value bang on.
Dave.
My band, Red For Dissent
Not really if, as I suspect the centre is common/earth and the others k1 and k2. The faff is that you need to swap the meter between the two but I guess since the connection can be well clear of the chassis, it could safely be 'hot swapped'?
Dave.
Sorry to reiterate , but hate to see people spending money unnecessarily, a full set as backup seems a bit over the top, as you have the option of EL84s or 6V6s on the output stage and 5 common pre-amp valves, ultimately your call of course
Ah! Not finding a map I did not realize the OP valve options. Ok so, no faff, just croc up for the valve of choice, if having both you will obviously power down for the swap.
Dave.
My new Victory V40 Deluxe has bias points and the adjuster on the outside of the chassis, points for V6+ Ground- and V5+ plus adjustment trim.
Is this safer, with less danger of death?
Almost certainly. I would need a schematic but suspect the test points come out via high value resistors and are thus not capable of delivering lethal current (the source voltage is very low anyway) .
BTW. ICBM and I agree to differ about external bias facilities. He is pro, I feel they invite fiddling and are an unnecessary added expense. But then maybe I am biased (ha!) because I would have been the poor slob that had to sort shedloads of maladjusted amps!
Dave.
My band, Red For Dissent
My band, Red For Dissent
http://www.egnateramps.com/EgnaterProducts/Rebel/Rebel30/Rebel30Specifications.html
Now to try and understand it properly
My band, Red For Dissent