Written by Frankie's side-kick.Quote:
Originally Posted by Andy40
Probably be a chapter on grave robbing.
cheers Mark.
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Written by Frankie's side-kick.Quote:
Originally Posted by Andy40
Probably be a chapter on grave robbing.
cheers Mark.
I'll have to try building a Tweed Deluxe one day, I think Evatco sell the chassis and eyelet boards for Tweed Deluxes, they also stock the transformers as well.
I got curious and had a look on good o'l Amazon.
Only one review so far but quite a knowledgeable one...including a quote that gave me a chuckle.
'Guitar players wanting to learn how tubes and tube amplifiers work.’ I will state that most or all of the musicians I know wouldn’t get ten pages into the book before they started getting cross-eyed.
cheers, Mark.
Apparently the author was shunned at the last IFSOIAAH (International Friendly Society of Igor’s And Associated Henchpersons) conclave.Quote:
Originally Posted by king casey
many have taken a dim view of his non traditional uses of electricity and his reluctance to promote reanimation of the dead for health and lifestyle benefits. He also suggested that more power is not always the answer, which really wound the society up. Igor (Igor, not Igor) was so shocked he lost his lisp and almost stood bolt upright.
If you don't like physics and math this book is not for you.
Damn I remember our eyes glazing over doing electronic theory at college, particularly in the first year when it was all new to us.Quote:
Originally Posted by Andy40
I mean you plugged your guitar into the amp, hit the power switch and magic happened in that big box, a pimply face kid didn't need to know how things worked.
What really made me get stuck into learning and understanding was drawing a circuit for homework on the train into college one day and this rather attractive young miss leaned over my shoulder and told me I had drawn a tetrode instead of a pentode and that type of valve didn't belong in that part of the circuit.
I was 15 at the time and I guess she was about the same age
Jaycar Electronics were selling a pretty good book called "Build Your Own Audio Valve Amplifiers" by Rainer zur Linde, it mainly deals with HiFi valve amplifiers, but it does have a section on guitar amplifiers too, it also includes lots of circuits, circuit board artwork and construction projects as well.
Attachment 30396
Did you marry that young miss Dave ??Quote:
What really made me get stuck into learning and understanding was drawing a circuit for homework on the train into college one day and this rather attractive young miss leaned over my shoulder and told me I had drawn a tetrode instead of a pentode and that type of valve didn't belong in that part of the circuit.
I was 15 at the time and I guess she was about the same age
Nah, she was far to intelligent to be attracted to the likes of me :DQuote:
Originally Posted by Marcel
There’s something seriously wrong with that book... too much damn reverb!
Attachment 30398
Dick Dale and Martin Cilia may disagree.Quote:
Originally Posted by WeirdBits
https://youtu.be/qmMeqid_fmU
Nice one Weirdy.Quote:
Originally Posted by WeirdBits
RIP Dick Dale, but all that spring reverb was bound to get you in the end..........
If only playe reverbs were portable........
Dick Dale did a pretty good version of Pipeline with Stevie Ray Vaughan, a mate of mine wants to do a cover version of it with me as part of a live gig performance.
I used to play Pipeline with the band I was in decades ago in my gigging days.
So much makes more sense now....
Tweed Era Model Number System
The first number indicates the decade: 5 = 1950's, 6 = 1960's.
The second letter indicates the cabinet type: A & B = TV Front, C & D = Wide Panel, E & F = Narrow Panel, G = Brown, Blonde or Black Tolex.
The third number indicates the model with 3 = Deluxe.
So "5E3" = 1950's Narrow Panel Deluxe.
Finally got around to lacquering that tweed!https://uploads.tapatalk-cdn.com/201...0b92c81e0d.jpg
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@ Andy40 Looks nice, bet it sounds really good too.
Progress update.....glaciers move faster than me....https://uploads.tapatalk-cdn.com/201...455051f3cc.jpg
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Hey Andy40, you've done some nice looking work on that eyelet board, looks nice and neat to me, that's going to be a big help when it comes to testing and troubleshooting the amp, and the way you explained the Fender amp model-numbering system makes a lot of sense to me too.
Yup, very nice work there Andy.Quote:
Originally Posted by Andy40
Remember to check everything, and when done check everything again....
@ Andy40 If you ever end up needing to order valves or new parts for your amp, there's a great company located in Australia called Evatco that you can order stuff online from rather than having to order from the US, here's a link to the Evatco website:
https://www.evatco.com.au/
thanks doc. 'll post a pic of the completed chassis tomorrow. I'll be firing her up tomorrow arvo so if I blow anything, I'll be ordering aprts from these guys.
Seeing as Evatco do have 5E3 amp chassis in stock, I'm going to look at buying all the parts needed to build a 5E3 amp next year, would be cool to have one so I can take it to the Nirvana club just up the road for a jam.
How do they suggest the initial firing up? I'd do it in stages. Start without any valves fitted, just in case there are some obvious shorts that take out the main fuse, then add the rectifier valve and test, then the pre-amp valves and test, then add the the power amp valves. (Don't forget to have the right impedance load connected).
Hopefully nothing goes wrong and you get a wonderful Deluxe sound.
First thing I would do after completing an amp build like this is to go have a good break to refresh, and then come back to it with a fresh mind, then I would check all the solder connections to make sure I hadn't made any mistakes, and then I would start doing all the test procedures prior to installing any of the valves.
Thanks doc and Simon. It took me a lot longer than expected. Doc was right taking breaks and coming back to check. I did find the odd mistake that way.https://uploads.tapatalk-cdn.com/201...92fe531d81.jpghttps://uploads.tapatalk-cdn.com/201...f5851431b4.jpg
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Simon. They do recommend that you check the voltages in stages. Unfortunately and weirdly without the full load of all tubes and speaker plugged in I was getting some really high voltage readings.
Anyway maiden schwang worked great. It sounded a lot better than I thought it would.https://uploads.tapatalk-cdn.com/201...d7796b5402.jpg
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With just the rectifier valve plugged in (I'm assuming it's a 5Y3 valve), the voltages will be higher than normal because the power supply isn't being loaded-down by the other valves, once the rest of the valves are plugged in you'll find that the voltages will drop-down to about where they should be, the two 6V6 power valves will be drawing the most current from the power supply out of all the valves together, on the other hand if the voltages were higher than what they should be when all the valves are plugged-in that would indicate that something is wrong, but since the amp seems to be sounding good, then it looks like it's all working as it's supposed to, but a good idea is to check the voltages with all the valves plugged in and compare them to what the assembly manual says they should be, it's okay if the voltages are a little-bit higher with all the valves plugged-in, but not significantly higher.
Yep you are right Doc.
Look the instructions require you to check certain voltages before you plug valves in.
Then check voltages after the rectifier (5Y3 - yes you are right) but as you pointed out it was heaps higher without any of the other valves plugged in.
Once the others and the speaker was plugged in the voltages were pretty good.
I muffed the Normal jacks somehow, I think I have a old solder joint there somewhere. I'm going to discharge the CAPS and fix it later or tomorrow when the wife's around.
A few questions for you doc:
I think I read somewhere that you have build some kind of bleeder that will bleed the caps to ground when you turn the amp off? or did I make that up?
I think i'm going to place an order for replacement valves from Evatco and another slow blow fuse, what brand of valves would you buy?
Its currently got JJ's in it
Quote:
Originally Posted by Andy40
Yes, you can make a special bleeder-probe to discharge the supply filter caps after you turn the amp off and completely disconnect it from the mains by un-plugging it, you can make a bleeder by attaching a resistor to a piece of wooden dowel, and then solder a piece of wire with an alligator-clip to one end of the resistor, the other end can either be attached to a small nail driven into the end of the wooden dowel or used as is, when you use the bleeder-probe to discharge the caps, the alligator-clip is clipped onto a convenient place on the chassis of the amp, which is normally securely tied to ground, the other end of the bleeder-resistor is touched to the positive terminals of the caps, I need to make a bleeder-probe since I'm going to be doing some amp-building work next year, I just found a piece of 8mm Oak doweling that I could use to make a bleeder-probe, dry-wood is a good electrical insulator, but you can also use a piece of PVC piping cut to a suitable length, a bleeder-probe is a handy piece of equipment to have when it comes to servicing a valve amp.
What I like to do while I'm discharging supply filter caps is to use a digital multimeter to monitor the voltage as I discharge the caps so I know that there aren't any dangerous voltages lurking in the amp circuits I'm working on.
Maybe I could start a thread about making a bleeder-probe, as I think it would prove to be quite useful.
When you choose a resistor for bleeding supply filter caps, you should pick a resistance value that's high enough so that you don't get a big spark when you touch it to the positive terminal of the cap, but low enough so that it bleeds-off the voltage quickly enough, you could probably use any value from about 10k to maybe 220k, and a power rating of maybe 1 Watt to 5 Watts, Marcel might be able to suggest a suitable resistance and power-rating for a bleeder resistor.
I've heard that JJ's are supposed to be a good brand of valves, although I've never tried them....yet, I've got a couple of Genelec E83CC Gold Lion gold-pin preamp valves installed in my Marshall MA100C amp and I think they are pretty good, although they did cost me about Au$50.00 each, I guess it really depends on how much you are willing to spend on valves, I personally wouldn't buy cheap valves since you never know when they'll go bad, and usually with no warning, Electroharmonix are supposed to be pretty decent, as are Sovteks, I read somewhere that Mullards are supposed to be some of the best valves you can buy but they tend to be pretty expensive, Shugangs are supposed to be good too, new old-stock RCA's are supposed to be pretty good too, generally, pretty much all the brands of valves that Evatco stock are good.
I've got a couple of Trigon 6SN7GT octal-base twin-triode valves that seem to be pretty good, and I just remembered that i happen to have one American-made General Electric 6V6GT valve in my stash of valves, I might use it to make a Fender Champ one day.
Anyway, I personally would try and buy the best quality brand of valves I could afford for any of my valve amps, depending on my budget, the better the quality of the tube/valve, the more expensive it's going to be, some audiophile-grade valves, like a new old-stock vintage 300B audio power-triode can cost quite a bit of money.
There's nothing wrong with doing what's called "Tube/Valve-rolling" which is basically trying tubes or valves of different brands in your amp till you find a brand that works for you.
Some of the valves in my stash of valves were scrounged from some defunct electronic equipment, I remember one time when I was studying electronics at uni in the mid 90's, they were getting rid of some unwanted stuff, and I managed to score myself a big box of miscellaneous valves for nothing but my time, including quite a few AWA brand 6CA7 valves, which are equivalent to EL34s, they were still in their original cardboard boxes, unused, wish I still had them now, there were also quite a few 12AU7As and 12AT7s, as well as 12AX7s, really kicking myself now that I didn't bring them with me when I moved to Darwin in 2000.
Going back to the bleeder-resistor, some valve amps, like Marshalls and Fenders, have a bleeder resistor permanently soldered in, in parallel with the power supply filter caps, this does two things I can think of, firstly, the resistors equalize the voltage across two electrolytic caps if the caps are placed in series to double the working-voltage of the cap, have a look at the power supply circuit of a Fender Twin and see if you can spot the two caps in series with the bleeder resistors connected in parallel, the resistors will be something like 220k in value, the two series-connected supply filter caps will usually be placed after the standby switch, the second thing that the bleeder resistors do is to bleed-off the voltage when the amp is powered-down as part of a safety feature, but it's always a good idea to check that there aren't any dangerous voltages remaining in the amp after it has been powered-down and completely disconnected from the mains supply, since bleeder resistors have been known to fail.
If you are making your own probe please shrink wrap it leaving only the tip to prevent unintentional shorts.
When I was in college a lifetime ago it was just a matter of shorting the cap with a screwdriver, brutal but effective and not recommended today.
Back then transistors were the future and ICs didn't exist ( who remembers hole theory for current flow )
Quote:
Originally Posted by dave.king1
Yep, good idea and I certainly will do that, cheers!!!
My amp tech (a chap I've started using this year for my Sound City amp head rebuild) recommends Sovtek valves. JJ are OK, but not as good as they were, and I know as a result that Blackstar stopped fitting them as standard a couple of years ago. But if they work and the amp's not noisy, and there are no microphonic or rattling valves, then there's really no point in replacing them for the sake of it.
I agree with what Simon said, if the JJs are working fine and aren't microphonic then there's no real need to swap them out, you can test each valve to see if they are microphonic by gently tapping the glass envelope with a pencil and listening for any ringing coming through the speaker, if a valve is microphonic it will tend to ring if it is gently tapped, some valves won't ring much and you might just hear a slight "tink" when the valve is gently tapped, some will ring a lot and be very sensitive to the point where you'll hear something coming through the speaker that sounds like feedback, generally the valve that has the first two triode gain-stages in it will be more susceptible to being microphonic, sometimes a power valve will become microphonic.
When a valve becomes microphonic it's usually caused by the internal electrodes becoming a bit loose in their mountings, this can happen when the valve is made at the factory, or it can happen over time from vibrations from the speaker, or when the amp is transported in a car.
One scenario where I would definitely swap out the valves is if one of the power valves starts to develop a red or orange glow on the plate, this is known as red-plating, I'd swap the valves if I'm absolutely certain that the bias circuit is working correctly and set to the correct bias voltage, there are no leaky coupling caps, all the socket pins are making good contact, and there are no other causes, like a shorted output transformer primary-winding, I would suspect a faulty power valve.
If you see a blue flourescence, or glow, inside the glass envelope of the power valves when the amp is fully powered-up, that's normal, if you see a lilac or pinkish glow inside the glass envelope of the rectifier valve, and the silver getter is turning a whitish colour, then it means that air has gotten inside it and the rectifier valve definitely needs replacing.
A preamp valve that has excessive hum should definitely be replaced.
There are in fact only three factories making guitar valves. Everything else is badging. Interesting read:
https://valvetubeguitaramps.com/valve-supplier/
Wow, what a fantastic response guys. Thanks so much.
Alright, I've got a bleeder probe. - stewmac has a "snuffer stick" that uses two 56k resistors in series.
The permanent bleeder as a mod was the thing I was thinking.
Anyway I'll have a go a trouble shooting this morning. If I have issues with the voltages, I'll post them.
Quote:
Originally Posted by Andy40
No worries at all, I'm only too happy to help out whenever I can, hope all the troubleshooting goes well and you end up with great sounding amp that works as it should, two 56k resistors in series (that gives a total value of about 112k) should work fine for discharging the power supply filter caps.
As Doc said, you can fit a permanent bleed resistor on the HT line, and on my amp builds I always do.
My go to is typically a 470k 1W from HT to ground at any convenient location. Often that will be near the main filter caps. If the HT voltage is around 300VDC then a 470k will draw about 0.6mA and develop 0.2W of heat .. On a 600VDC HT rail I will put a 1M 1W resistor which will draw again about 0.6mA but will develop about 0.4W of heat... (E=I*R, P=I2*R)
Remember that the entire HT rail is connected by a DC path so putting a 470k resistor on the common HT distribution point of the preamp stage (where voltages are often around 300VDC) is just as effective as a 1M on the main filter cap (where on larger amps can be in the 600VDC range), only difference is the ultimate safe discharge time with the resistor on the preamp is it will take near twice or four times as long....
One must always remember too that the permanently fitted bleed resistor is drawing current, which may change some HT rails nominal voltage. On a Marshall design the step down resistors for each stage from power amp stage to preamp are cascaded (or in series if you prefer), so that extra 0.6mA of essentially wasted HT power will draw down the HT power available to the preamp should you put the bleed resistor there. An extra 0.6mA going through those two typically 10k HT dropping resistors that feed V1 and V2 may not sound like much but it can change the whole character of the Amp for the better or the worse, so be aware
Doc's clip on 56k is great as it will get rid of most of the charge on those filter caps pretty quick, and render the amp fairly safe in a short time to allow a safe servicing environment. But resist the temptation of fitting a 56k 5W resistor permanently..... 56k at 450VDC is 8mA which is a significant percentage of what most guitar amp HT power supplies can create in the first place, and with 3.6W of pure heat being generated from this one resistor inside the amp case is simply a waste of energy. In the case of a Blues Junior amp from Fender the HT supply can at best only give around 120mA so 8mA is theft of near 10% of the amplifiers potential noise with nil benefit to the player...
Quote:
Originally Posted by Marcel
Yep, a typical 12AX7 triode gain-stage as found in a Fender or Marshall amp tends to draw about .005 mA of current, that's 5 micro-amps (or maybe as much as 1mA depending on the values of the cathode and anode resistors since they determine the maximum saturation current) from the power supply when it is fully turned-on or saturated (going by what I've seen looking at a characteristic graph of a 12AX7 in a valve manual) assuming that the plate voltage is from about 250VC to 300V DC (the 12AX7 is designed to work with plate voltages of a maximum of 300V DC) , 8mA is significantly more current than .005mA so I can see why it would change the character of the amp, due to loading effects.
Sorry if I'm going off on a bit of a technical-tangent here.