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Teahead

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Everything posted by Teahead

  1. Cheers Myles, funnily enough I had looked at both of those. Nice to have your approval all the same. Take care!
  2. Hey Myles. Wondering if you could suggest a brand of NOS ECC83 I could source to use in V1 of a Cornell 18/20 Plexi combo? I have Sylvania Black Plates and various NOS examples but all prove too microphonic in V1 of that amp and caused problems. I have some current production GT ECC83 valves that are silent in V1 and causes no issues, but would still like to experiment with NOS flavours without the microphonics. I have been recommended to look at short plate examples, having been told they are best suited to amps such as mine which are troublesome with microphonic preamp tubes. Can you confirm I might have better luck with these and maybe recommend one or two to look out for? Many thanks and best wishes, Tea.
  3. I have another pair of speakers I could try, but I'll need to get them wired in series before I can try it out. I have a 1/4" plug on my speaker cable to use with a Hotplate, so no troubles there.
  4. I only wish I was near you, Myles. Three thousand miles of Atlantic Ocean and the width of the American continent lies between us, or to put it another way, I'm in Ireland. I did pull the chasis and try what you've suggested, neither seemed to solve the trouble. How might I inspect to rule out speaker buzz? I was running the amp through a Hotplate and the buzz didn't seem to get louder when the gain was increased with attenuation applied. It did get louder when the physical volume increased though. Could this indicate speaker trouble? Thanks for your help.
  5. Hi Myles, been having some trouble with a nasty 'buzz' on only one or two notes through my AC30. Swapped power tubes to no avail, should I look to the rectifier or the preamp tubes next? Thanks.
  6. I love their Axiom series in these amps. Mmm, they only seem to offer Axiom Power Transformers for the AC30. The only OT's listed are Tone Clones. I'll shoot them an email and work it out from there... Thanks again for your help, Myles!
  7. Thanks Myles. Oh, would any particular model be best suited in your opinion? Albion, Hadden & Woden mean little to me!
  8. Hi Myles, I'm considering buying a Hoffman Board Upgrade for my 2003 AC30tbx reissue. Just wondering if you're familiar with what they do. Here's a link to the supplier... http://www.tonezoneonline.com/boards.html Is this an advisable upgrade? Would it be more of an improvement in reliabilty or tone? Perhaps I would get better value from spending the money elsewhere on the amp, such as replacing the OT with a MM version? I already have a few sets of nice nos tubes that I love to hear in this amp, but as it's my one and only workhorse, I'd like to get the most from it and hopefully make it more reliable in the process. Many thanks for your help & advice... Tea.
  9. Hi Myles, hoping to avail of your wisdom once again, please excuse me if this post becomes a little long winded... My '04 Reissue AC30tbx has a nasty little habit of blowing the rectifier and fuse, I only got around 60 hours from the last two I used. It happens at power up and to be safe I also change all the power tubes when it blows. On two occasions, I've found that the grid resistor relating to one of the power tubes has been scorched to a cinder, it's R73 on the schematic. I had it replaced the last time and it's in the shop again for repair as I type. I've spoken with guys who own the same amp and who operate it in much the same way. Everyone has experienced the problem I am suffering, but they seem to get a couple of years from power tubes and a rectifier, where I am only getting a couple of months. Could you suggest where a tech might look for the cause of this? Folks have told me that something could be pulling too much current? Is there any risk in using a Weber copper solid state GZ34 replacement? Considering the circuit appears to have such an appetite for rectifier destruction! Finally, when the GZ34 blows, does it take the entire quad of EL84s with it, or just the power tube relating to that specific socket where the resistor has scorched? I had four Brimar output valves in there when it happened last and I'd love to hope that three of them might be ok! Thanks for your help, Myles!
  10. Thanks for your help above Myles, I'm about to try some dampers in my Korg RI AC30tbx, I get some microphonic noise with one or two notes on the fretboard. It happens with any and all tube swaps I've tried and it's finally pushed me to look for a solution. The noise isn't present when I remove the chasis, so I'm hoping dampers like these will help when it's mounted in the combo? Now, the question is, what about the retainer clips on the output & rectifier tubes? I'm kind of presuming these are essential to the trouble free running of the amp, with the horizontal mounting? Or are they? They seem to worsen the problem, so I would like to remove them altogether, or is this a bad idea? If so, are there alternative kinds that will fit my amp and accomodate the tube dampers I'm looking at? I'm pretty sure the stock ones aren't going to be suitable. Or should I be looking at alternative dampers that can be used with the existing clips? Apologies for the long post, many thanks to you for sharing your wisdom here... tea.
  11. Hey Myles, thanks for the response and information. I must have been editing my post when you were typing your reply(!) If you don't mind checking back to my original post a moment? Basically, I've since found the rectifier to be a source of excessive idling noise and rather nasty amp tones, but have replaced both it and the EL84s, just to be on the safe side. Since doing this I've had no issues at all, it's running great. I suppose I should send the suspect Brimar EL84s off to Derek at Watford Valves and have him check them out? Do you think it's more likely the rectifier would have harmed the output tube and resistor, or vice a versa? Thanks again!
  12. Hey Myles, My '04 Korg Reissue AC30tbx blew a fuse the other evening, after about thirty minutes of rehearsals. Upon further inspection I noticed R73, which I'm led to believe is a screen resistor relating to one of the output tubes, was "chipped" and had a small amount of scorching around it on the pcb. I took it to the shop where the repair guy replaced the resistor and now the amp seems to be working fine, with all the same tubes it had when it failed. Should I replace these tubes with my spares? Just to be safe? I don't want to run the risk of this happening again and if there's any chance the Mullard GZ34 or Brimar 6B5Q's are responsible I'd sooner swap them out. What else could have caused the resistor to end up like it did, if not tubes? Many thanks... Tea. edit... I've just ran the amp again, with the chasis removed and after ten minutes I noticed some nasty tones, there was lots of noise coming from the rectifier. I swapped the rectifier and all was well again, sounds better than ever in fact. I also then replaced the power tubes, just to be safe, but replacing the rectifier seemed to completely solve the problem by itself. Should I try the other EL84s again in a few weeks, or maybe try to get them tested before attempting anything with them? Could this suspect rectifier have caused the damage to the resistor? Or to the power tubes?
  13. I had very similar troubles, which turned out to be a preamp tube that was loose in its socket due to short pins. It only happened when I turned up as the vibrations were unseating the tube. So it might also be worth swapping a preamp tube or two if the cable checks out? Good luck... Tea.
  14. Hi Myles. I just wanted to ask your opinion on upgrading the output transformer in my Korg Reissue AC30tbx and maybe lowering the filter caps too. I've considered the replacement boards that are offered, but I had been advised that... Quite a few AC30 enthusiasts have recommended upgrading the O/T, is there anything unwise or particularly risky about having this done? Thanks for your help... Tea.
  15. Hi Myles, I have picked up a NOS Mullard GZ34 from Germany quite reasonably priced for my AC30, plus a pair of Groovetubes "Mullard" ECC83 and a quad of UK Brimar EL84s from Derek at Watford Valves. Added to the '64 Grey Alnico T1088 speakers I found, the amp is sounding sweeter than ever. I'm settled on the Normal Channel as my tone and so I would like to remove the "idle" tubes. Is this ok? Will I put any extra strain on the remaining tubes? Thanks for your time Myles. I appreciate your advice. Tea.
  16. Thanks Myles! My heart rate and blood pressure are falling already! Your reassurance is much appreciated, cheers for your time, I think I owe you a cold beer sometime! Tea.
  17. Bob at Eurotubes gets a thumbs-up from me too! He made me Deville sound better than ever. A great tube guy! Myles, I'd like to ask your advice on something. I was experiencing a "whistle" or "consistent tinkle" from my Korg AC30tbx that bloomed behind certain notes on the fretboard. It decayed quite naturally and I presumed it to be a tube problem. When I removed the back panel to check them, I discovered what I'm told is One of the two parallel 100ohm /5W resistors that provide the cathode biasing for the el84's, to be removed from the board and lying loose inside the chasis. It's marked R71 on the PCB, where it should have been(!) I'm in a bit of a dilemma now. Could I have damaged the amp by using it this way for the past dozen practice hours in the last month? What in particular may I have strained? It seems fine, apart from the "whistle" that led to me finding the resistor loose, I had no other cause for concern. The "whistle" may or may not have been attributable to the loose resistor, but I won't know until I can get it replaced. What course of action would you advise. The amp is still under warranty, being four to five months old. Would if be sufficient to have a competent tech solder "R71" back inplace and check for any signs of wear? Or should I bite the bullet and send it in for repair with Korg under the warranty. I'd hate to do this, only to have them solder the component on and return it with a huge shipping bill, but I want to be sure not to risk my amp. Thanks for any advice you can offer here Myles. Oh and please tell Jimmy that his replacement board is looking more and more like a great idea! Tea.
  18. Thanks Myles! I have it downed. I understand your reluctance to recommend something that comes down to personal tasete. Thanks for the pdf. Tea.
  19. Hi Myles! Just wondering if you could point me towards a good mic for my amp and perhaps occassional vocals? I've been looking at the AKG C 3000... http://www.dolphinmusic.co.uk/d2/shop_image/product/6aba0e7b27c498bf8dea226b1dd85cbb.jpg It's £150 with cable and boom, which is around $300 at the current exchange rate. Could I perhaps get a better deal on a mic in the States? If so, what would you recommend? I currently own an AKG SM58 "clone" and I'm thinking of a condenser mic to use along with the "SM58" to allow me to try and better my recorded tone. Thanks for listening! I appreciate your advice. Tea.
  20. Thnaks for your advice, Myles. I'll get the amp checked before I put the new quad in there. The replacement should arrive before Friday so I'll let you know what the outcome is. Thanks agin, Tea.
  21. Myles, thanks once again, the schematic was a great help to me. I now feel like I almost understand what's happening in there. However, I've encountered one other problem. I got a matched quad of "Harma STR EL84s" from Watford Valves this morning, along with a few JJ Tesla ECC83s. I replaced the valves and switched the amp to standby, only to notice that one of the four output valves was lit very dim compared to the other three. I switched the amp off and called Derek at Watford for some advice. He said I really should have checked the bias, something I know nothing about, but agreed to send a replacement as the valve never appeared to work correctly, whilst the other three were fine. I had been told on a Vox forum that a bias check wouldn't be necessary, was that wrong? Could I perform this adjustment myself with the right guidelines and the right tools? Or should I leave it to a tech? For the time being I have three of the Harma valves in there, with one JJ Tesla. Could this be damaging the new valves? Sorry about all the questions Myles, I'd appreciate any assistance you can offer. Tea.
  22. Hey Myles. I've ordered some NOS EL84s from Watford Valves along with a few JJ 12AX7s to use in my AC30. I'm just wondering. Using this picture as a guide, which pre-amp valves relate to which particular job? http://www.voxshowroom.com/northcoast/images/products/new_amplifiers/ac30service/chart.jpg Thanks for your help! Tea.
  23. Here's some of the advice Myles gave to me when I was in a very similar situation. Check out this link to THDs "Yellow Jackets." I used them in my Hot Rod Deville and they do an excellent job of reducing the output of the amp. They will change your sound a little, the amp will break up earlier and will have more lower midrange to the sound. Consiberably quieter in the amp than the stock output valves, and to me they were "thicker" in tone. But, they're easy to install, cheap and quick to change back! THD also do a "Hotplate" attenuator. Click "here" for a link. Like the Dr. Z "Airbrake" this goes between your power amp and your speaker to "soak" the power of the amp at full tilt and allow volume reduction to playable stage levels. THD to a different coloured plate for specific Ohms ratings, where the Dr. Z Airbrake is suitable for almost any amp, making it a much more versatile piece of gear. The attenuators will affect your tone too, but in a different way to the Yellow Jackets. I used a Hotplate for a while with my Deville, but ultimately I achieved better results with the Yellow Jackets, which are much cheaper. I fell in love with the EL84 tubes so much I changed my amp for a Vox AC30! This is all down to personal taste though, you should try all the options you can and see what works best for you. Tea.
  24. Hey Myles, you recommended the 5V4 rectifier lately for my AC30 reissue. When I phoned Watford Valves the guy advised against me using it as it would invalidate my warranty. Is it perfectly safe? Is he just being over cautious? Also, I heard that a 5Y3GT as a rectifier would be safe as the reissues have a standby switch to protect the tube on power up. Apparently this causes more voltage sag than the 5V4, and exaggerates the effects on tone that it has. Have you tried one of these in an AC30? With your approval I'm going to get one of each of these to try out. Can I do some damage to my amp? Thanks for your help, Tea.
  25. Hey Myles, just wondering if you could advise me on a rectifier swap for my Korg AC30tbx. I've been told that you can safely put a 5V4 in there for a little lower plate voltage and a little more sag. It will "brown" the sound a little but leave plenty of chime. How much of a headroom reduction would this give, if any? I'm struggling not to buy an attenuator, as I had a dislike for the effects of a Hotplate on my Hot Rod Deville. Is it worthwhile changing the rectifier in the hope of reducing headroom? Or should I try a Dr.Z Airbrake? I've been told it yields better results than the Hotplate? Thanks for your time Myles. Tea.
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