Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: kwm488 on June 04, 2014, 02:37:53 pm
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hi
i plan to build ac30. i bought the weber 6v30 kit. but i am confuse. weber layout look like little different with vintage ac30. and ac30 have many version. some is 5 preamp tube, some is 6 preamp tube.
and i want to build top boost version. but it seem have few top boost version. i just find 2 ac30 layout only.
can anyone give me some suggestion?
and i want to know where can i buy the ac30 trem and speed pots. it look like special.
thanks
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can anyone help?
i want to build ac30/6. but i can't find a correct layout.
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You have a Private Message
K
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hi
thank you. you help me a lot a lot. thank you for your help.
sorry, i have little question. about the speed switch and vib switch. is this fit? or have any better suggestion?
http://www.tubeampdoctor.com/product_info.php?category_id=55&products_id=1571&mySID=eIHWFIg6YzN1Vsj2QsCis3 (http://www.tubeampdoctor.com/product_info.php?category_id=55&products_id=1571&mySID=eIHWFIg6YzN1Vsj2QsCis3)
and i am still finding vox ac30 style indicator light, do anyone know where can i buy it?
i built fender and marshall amp. but this ac30 is very difficult for me. very difficult to find the parts and layout
and i don't understand why weber ac30 layout is quit different. for example, weber suggest use 1M pot for speed and vib, but i can't find any pot 1M with switch.
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http://www.tube-town.net/ttstore/Potentiometer/Alpha-Potentiometer-16-mm-PCB/Potentiometer-Alpha-16-PCB-1M-Log-DPDT::4658.html (http://www.tube-town.net/ttstore/Potentiometer/Alpha-Potentiometer-16-mm-PCB/Potentiometer-Alpha-16-PCB-1M-Log-DPDT::4658.html)
http://www.tube-town.net/ttstore/Potentiometer/TT-Potentiometers/TT-Potentiometer-24-mm-1M-Log-w-Switch-SPST::5315.html (http://www.tube-town.net/ttstore/Potentiometer/TT-Potentiometers/TT-Potentiometer-24-mm-1M-Log-w-Switch-SPST::5315.html)
http://www.tubeampdoctor.com/en/shop_Potentiometer_Push_Pull_Pots/ (http://www.tubeampdoctor.com/en/shop_Potentiometer_Push_Pull_Pots/)
K
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1M with on/off switch, CTS and Alpha.
http://hoffmanamps.com/MyStore/catalog/parts5.htm (http://hoffmanamps.com/MyStore/catalog/parts5.htm)
Brad :icon_biggrin:
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hi kagliostro (http://el34world.com/Forum/index.php?action=profile;u=1588)
i don't need 1M pot with switch if i follow the layout which you sent to me, right?
and i really don't understand , even the ac30 ptp board, i can't find it.
i just find this small piece board, and i cut it and glue it.
and i am still finding correct ac30 inductor light, resistor etc........... do anyone know where can i buy it?
(http://i23.photobucket.com/albums/b383/kwm488/20140606_121339_zpse9v2brfs.jpg) (http://s23.photobucket.com/user/kwm488/media/20140606_121339_zpse9v2brfs.jpg.html)
(http://i23.photobucket.com/albums/b383/kwm488/20140606_115051_zpscm6dtgub.jpg) (http://s23.photobucket.com/user/kwm488/media/20140606_115051_zpscm6dtgub.jpg.html)
(http://i23.photobucket.com/albums/b383/kwm488/20140606_115112_zps2x6hh4tq.jpg) (http://s23.photobucket.com/user/kwm488/media/20140606_115112_zps2x6hh4tq.jpg.html)
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http://www.tube-town.net/ttstore/Transformer/Chokes/Hammond-Guitar-Series/Hammond-194E-Choke-AC30-vintage::2104.html (http://www.tube-town.net/ttstore/Transformer/Chokes/Hammond-Guitar-Series/Hammond-194E-Choke-AC30-vintage::2104.html)
K
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hammond transformer is good too. but i never try it. hope i have choice to try in future.
btw, i want to buy
vintage look vox footswitch
vox style inductor light
do anyone know where can i buy it?
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and what is the name of this ? where can i buy it?
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http://www.radioshack.com/product/index.jsp?productId=2103986 (http://www.radioshack.com/product/index.jsp?productId=2103986)
http://it.mouser.com/Search/ProductDetail.aspx?R=39100-0912virtualkey53810000virtualkey538-39100-0912 (http://it.mouser.com/Search/ProductDetail.aspx?R=39100-0912virtualkey53810000virtualkey538-39100-0912)
http://www.ebay.co.uk/itm/VOX-AC30-PILOT-LAMP-HOLDER-POWER-INDICATOR-4-VALVE-GUITAR-AMP/360950934709?_trksid=p2047675.c100011.m1850&_trkparms=aid%3D222006%26algo%3DSIC.FITP%26ao%3D1%26asc%3D20140107083358%26meid%3D7421734894070317883%26pid%3D100011%26prg%3D20140107083358%26rk%3D1%26rkt%3D10%26sd%3D360738983807 (http://www.ebay.co.uk/itm/VOX-AC30-PILOT-LAMP-HOLDER-POWER-INDICATOR-4-VALVE-GUITAR-AMP/360950934709?_trksid=p2047675.c100011.m1850&_trkparms=aid%3D222006%26algo%3DSIC.FITP%26ao%3D1%26asc%3D20140107083358%26meid%3D7421734894070317883%26pid%3D100011%26prg%3D20140107083358%26rk%3D1%26rkt%3D10%26sd%3D360738983807)
http://vintageamps.com/plexiboard/viewtopic.php?f=2&t=105806
I'm using this style of pilot lamp for my ac30 build. It's 120v so you can wire it directly to your power/mains switch. No need to run heater wires. You can find these in many different places. I sourced mine from my local electronics store.
(http://www.electronicplus.com/images/products/B6010M1.jpg)
K
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thanks
you know everything about ac30
and do you know where can i buy this? can i find it in RS or mouser?
it is look like 8 or 9 pins.
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http://hoffmanamps.com/MyStore/catalog/parts12.htm (http://hoffmanamps.com/MyStore/perlshop.cgi?ACTION=enter&template&thispage=BoardBuilding&ORDER_ID=!ORDERID!)
Scroll down
K
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thank you.
how about this, where can i buy it? it is hold the capacitor to the chassis
thanks
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Seems that Doug sell only the vertical version
http://hoffmanamps.com/MyStore/perlshop.cgi?ACTION=enter&template&thispage=Capacitors&ORDER_ID=!ORDERID! (http://hoffmanamps.com/MyStore/perlshop.cgi?ACTION=enter&template&thispage=Capacitors&ORDER_ID=!ORDERID!)
I think you can easily build a pair of those clamps for horizontal clamping cutting a thin foil of aluminium or copper or galvanized iron
if you do a google (search for capacitor clamp) you can find those clamps, the difficult part is to find those that fits in measure your electrolytic
this has the appropiate form, but I doubt you have a 2" capacitor
http://www.chiefaircraft.com/ms-21919dg32.html (http://www.chiefaircraft.com/ms-21919dg32.html)
K
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KWM488
Please check my store here first if possible
http://hoffmanamps.com/MyStore/catalog/partsenter.htm (http://hoffmanamps.com/MyStore/catalog/partsenter.htm)
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hi
thank you for the link
btw, i am confuse of the layout.
kagliostro,
your layout mention ac30/6TB have treble, normal and bass version. which one is better? is the bass version for bass guitar?
and in the layout, it is never mention the treble and bass pot value. but in the weber layout, it is 1M. in fact, is weber layout is not 100% follow vintage ac30? i am confuse, and i need to order the pot soon.
sorry for too much question. it looks like very difficult to find the ac30 clone information
thanks
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hi
and i am confuse again.
i see your schematic, the treble and bass pot should be 500k.
but i see here. the treble and bass is 1M . so which one is correct
http://www.blueguitar.org/new/articles/other/topboost.pdf (http://www.blueguitar.org/new/articles/other/topboost.pdf)
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There where different version of the amp for different purpose
so you must realize it in the version that inspires you more, then you can try the other small variations on the theme
K
p.s.: Some years ago I verified the Weber layout and, for what I can remember, it is pretty close to the original, also if not perfectly
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Hi
Understood
But sorry, please forgive me. In your zip file, it mention bass, normal and treble version different cap and resistor value. But it never mention bass and treble pot are 1M.
Do you mind to help me, the 1M bass and treble pot is what version ac30/6TB
I am newbie of vox. I built fender and Marshall all the way
Thanks
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And i never see people say bass and treble pot are 500k. But i find out someone say it is 1M
http://archive.ampage.org/threads/4/gadc/253846/Re_Stupid_Vox_AC-30_question-1.html (http://archive.ampage.org/threads/4/gadc/253846/Re_Stupid_Vox_AC-30_question-1.html)
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for your purchases I can recommend you Doug's store
for deep details on Vox amps
http://vintageamps.com/plexiboard/viewforum.php?f=2&sid=96e48f2f1cadc215cee9dc5d7b1951d4 (http://vintageamps.com/plexiboard/viewforum.php?f=2&sid=96e48f2f1cadc215cee9dc5d7b1951d4)
K
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thanks.
and i will upload my project photo here. hope to share more ac30 clone to everyone.
thanks
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I don't understand
Weber sells a kit and they do not provide a layout diagram or assembly instructions?
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sorry kagliostro (http://el34world.com/Forum/index.php?action=profile;u=1588)
my wrong. the top boost treble and bass pot must 1MA, i see a wrong thing in your file. the file say it is 500k for the trimmer which on the board.
and weber don't have any instruction , just layout and schematic. but i compare weber layout and the vintage ac30. it looks different .
do you mind to take a look. i am newbie of ac30. ac30 looks like have a lot of version.
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Hi kwm488
I think EL34 would like to have an answer to the question he put
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As I told, some years ago, I compared the AC30 schematic with the 6v30 schematic and they were pretty close if not the same
however Weber layout is a bit different from Vox layout, I don't know if Weber do that for particular reasons, but so it is
K
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hi
thank you
honestly, i have big problem about building ac30 now. i need to order a ac30 combo cab. do you know who can make a raw ac30 combo cab?
the worse case will be, i make it by myself. do you have any instruction or information about ac30 cab? vintage ac30 use Baltic Birch Plywood , right?
thanks
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I'm not a wood expert, however
K
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hi
i have that pdf file. but i hope to know more information. for example, what wood do vintage ac30 used? and do you know which USA guy or company can make that cab for me. i ask few person already. all reject to do it
btw, do you know what is the name of this parts? where can i buy it?
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I'm not able to see what is that, a better resolution picture is required
(seems to be a simple wire connector, but I'm not sure)
K
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hi
better photo attach.
i think it is the mount for the wire. what is the name of this tools? where can i buy it?
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It's just a terminal block
Why do you think you need that exact item?
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Hi
I hope to build the amp more close to original. And this item is good, i don't need to drill the chassis
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Post #9, you asked about that there and in post #10 there is the answer
http://www.radioshack.com/product/index.jsp?productId=2103986
http://it.mouser.com/Search/ProductDetail.aspx?R=39100-0912virtualkey53810000virtualkey538-39100-0912 (http://it.mouser.com/Search/ProductDetail.aspx?R=39100-0912virtualkey53810000virtualkey538-39100-0912)
K
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hi
sorry , wrong photo
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Ah, OK, that is a metal clip retainer, now they are common in plastic
http://www.partsreplacementstore.com/product/TRail_Wire_retainer_Clips (http://www.partsreplacementstore.com/product/TRail_Wire_retainer_Clips)
(http://www.partsreplacementstore.com/images/company_assets/e9259636-56c2-445c-9b5f-5ebd746f40f3/product_catalog/ROA-TRAILSTR-Rail-Wire-Reta_thumb.JPG)
I think that metal version is not more disposable or difficult to be find exactly like that
see here
http://www.efc-intl.com/products/spring-clips-metal-cable-clips-edge-mount-for-bundles.htm (http://www.efc-intl.com/products/spring-clips-metal-cable-clips-edge-mount-for-bundles.htm)
(https://encrypted-tbn3.gstatic.com/images?q=tbn:ANd9GcTQ5fzbjqIlGitF5vdYo-FkxHFMFGZJIIZJltSuvBBAcR2J9-XV)
K
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hi
do you know what brand of this dog bone caps
thanks
sorry , EL34. it is misunderstand before. i will use output jack for speaker connection
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I've no brand to give you
However those are tube ceramic capacitors (to me)
K
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hi
do anyone can teach me?
why ac30 heater is short to the ground.
please see the photo
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Don't look to that layout, a guy in an italian forum build an amp following that layout and found some mistakes on it that must be corrected
May be (you must control it) version 7 is correct, but version 5 isn't
EDIT: I revised that connection with the layout draw by Stephen Grosvenor in 2005 and effectively seems correct, however my council is to don't
use that connection at all
K
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HI
But i sure ac30 heater is short to ground. Because i saw it in all vintage ac30 ,and you send me ac30 layout , heater is short to ground too.
But i don't understand why
Anyone can teach me?
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hi
my amp is almost finish.
just need to wire the rest of power section wire and double check. hope no any error
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The vintage AC30's had a few problems with how they were made, and shorting one side of the heater to ground is one of them. Some of the older Fenders like my 1956 5E3 are wired this way also, and it is simpler to wire it that way but results in more hum every time. You would want to wire up the heaters like Fender did it in their blackface amps as it will result is less hum.
There are lots of Fender kits out there but AC30 kits are not as easy to find, especially something that is the same as a vintage one. There are many reasons for this, but a couple are that AC30's were not as widespread as Fenders; AC30's had some issues with how they were made that require changes to get better performance such as the heater connection as mentioned above; the chassis arrangement is unique to Voxes; the circuit is quite complicated when you also have the tremolo and vibrato circuits included.
I would suggest that you get the Vox Amplifiers: The JMI Years book by Jim Elyea. It has everything you ever wanted to know about vintage Voxes including schematics, histoary, parts used etc. Here is a description of the book >> http://www.premierguitar.com/articles/Vox_Amplifiers_The_JMI_Years. (http://www.premierguitar.com/articles/Vox_Amplifiers_The_JMI_Years.) You can do a search at Amazon or elsewhere to buy it. It is an expensive book but it is HUGE and is the best book anyone has ever done about an amp company. They have all the JMI era Vox amps in there too, not just AC30's.
The signal caps used in many of the originals, and in the picture you linked (gold with a red stripe) are Wima Tropylfols. I have some that I got at surplus places in 0.22uF and 0.1uF values, but they are hard to find for other values at surplus places. You can find them on ebay from time to time but they are not cheap. They are good quality and good sounding caps though, but any modern cap such as a Sozo, Mallory 150, etc., are likely as good or better.
Greg
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hi
thank you for your suggestion.
btw, i wired my amp all wire. and the amp is sound great.
my MM PT have heater CT. i try to remove the pin 4 5 to ground, and ground PT heater CT. but sound changed after i do it. i don't like it. so i use back the vintage vox method.
about capacitor , i try to use sozo for my marshall superlead. and i change it to vintage mustard finally. i can say vintage capacitor sound much much more better.
btw, do anyone have vintage wima TFF 0.047uf 400v and durolit 0.15uf 630v for sell? i want to buy it
thanks
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hi
i finished my ac30 clone. i think it is perfect. but when i dial the brilliant over half level, i get white noise.
is this normal? because i never own vintage ac30. and some people said that vintage ac30 have a lot of hum because their design have problem.
i don't sure , do anyone mind to help me?
and i 100% follow vintage ac30 to clone it. i used vintage wima caps, vintage erie resistor, vintage made in england filter caps. vintage made in england wire.
i finish my ac30 clone. but i have white noise, is it normal (http://vintageamps.com/plexiboard/viewtopic.php?f=2&t=107796#p1037306) (http://vintageamps.com/plexiboard/styles/prosilver_se/imageset/icon_post_target.gif) (http://vintageamps.com/plexiboard/viewtopic.php?p=1037306#p1037306)by kwm488 (http://vintageamps.com/plexiboard/memberlist.php?mode=viewprofile&u=26183) on Wed Sep 03, 2014 3:28 am
hi
i finished my ac30 clone. i think it is perfect. but when i dial the brilliant over half level, i get white noise.
is this normal? because i never own vintage ac30. and some people said that vintage ac30 have a lot of hum because their design have problem.
i don't sure , do anyone mind to help me?
and i 100% follow vintage ac30 to clone it. i used vintage wima caps, vintage erie resistor, vintage made in england filter caps. vintage made in england wire.
(http://i23.photobucket.com/albums/b383/kwm488/2014-08-28164400-1_zpse279796f.jpg) (http://s23.photobucket.com/user/kwm488/media/2014-08-28164400-1_zpse279796f.jpg.html)
(http://i23.photobucket.com/albums/b383/kwm488/2014-08-28164245_zps752a7493.jpg) (http://s23.photobucket.com/user/kwm488/media/2014-08-28164245_zps752a7493.jpg.html)
and the video link is here.
http://youtu.be/L33txJtSDtw (http://youtu.be/L33txJtSDtw)
thanks
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Very nice.
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Thanks
Btw, when tge brilliant vol to half, i get white noise. Is it normal?
Thanks
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probably
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I cannot seem to find the actual schematic you used posted. Did you use shielded wire for the wiper of the Brilliance pot and ground on lug 3 of the pot? Does it change when chopsticking? If it does, you can do something about it. I can't really tell how loud it is, but I usually go by the simple rule on floor noise.
The Brilliance circuit is different in your build than my AC15 and I cannot seem to find a readable schematic, but I would simply turn it up and poke around to see if I can find something that makes it change and address this if you find something.
BTW, great looking build!
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For the electrolytic caps, did you use new ones or vintage ones? Using used electrolytic caps isn't a good idea as those type of caps go bad with time, and go bad even quicker if they are not used. Using bad electrolytics could cause possible problems with the amp.
AC30's do not use a negative feedback loop so as the volume is turned up they will be louder than a typical Fender amp in comparison when considering the background noise and hiss. An AC30 wired like the vintage ones as far as the heater connection will also exhibit more background hum than an amp wired with an artificial center tap on the heaters.
Greg
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hi
i think my ac30 white noise is normal. but if someone can prove it. it will more perfect for me.
i try to use the PT heater CT , so i don't ground one side heater. but i don't think the noise level different. both are same.
sorry, this is my first EL84 amp. i have some question. do anyone can help me
1. can i use two EL84 for this amp like fender marshall? i just try it with 2 EL84. but that two EL84 super super hot even my amp just turn on few minutes.
2. can i add 1ohm resistor for EL84 tube socket like marshall fender amp. so i can know the tube bias.
3. the brilliance channel have white noise when i turn the amp about 2:00. and if i adjust the bass and treble , noise level will different. honestly, i think this should be normal. but i really hope someone who own vintage ac30 amp can prove it for me
thanks
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1. can i use two EL84 for this amp like fender marshall? i just try it with 2 EL84. but that two EL84 super super hot even my amp just turn on few minutes.
Yes. But since it's cathode biased you will need to change the cathode resistor to 130Ω when you pull two tubes.
2. can i add 1ohm resistor for EL84 tube socket like marshall fender amp. so i can know the tube bias.
Yes. See page 2 of the following pdf for an example...
http://home.comcast.net/~seluckey/amps/VAC15/Vox_AC15.pdf (http://home.comcast.net/~seluckey/amps/VAC15/Vox_AC15.pdf)
3. the brilliance channel have white noise when i turn the amp about 2:00. and if i adjust the bass and treble , noise level will different. honestly, i think this should be normal. but i really hope someone who own vintage ac30 amp can prove it for me
I think it's normal but I can't prove it.
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thank you.
sorry for once more question.
i used two el84 for few minute without change the cathode resistor to 130ohm. will that two EL84 dead or hurt?
that two tube very hot. and have little smell. i stop immediately.
btw, that is mullard
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They were definitely stressed. I would not think they are dead. Hard to say if they were harmed, but probably not. Did they redplate?
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Hi
No red plate. But the tube is very hot.
So isl it hurt?
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They were definitely stressed. I would not think they are dead. Hard to say if they were harmed, but probably not. Did they redplate?
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No redplate
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the cab is arrive today. i wait it 2 months. it is very very nice.
(http://i23.photobucket.com/albums/b383/kwm488/20140924_131619_zpsftfurtlu.jpg) (http://s23.photobucket.com/user/kwm488/media/20140924_131619_zpsftfurtlu.jpg.html)
(http://i23.photobucket.com/albums/b383/kwm488/20140924_131725_zps6kokdk4p.jpg) (http://s23.photobucket.com/user/kwm488/media/20140924_131725_zps6kokdk4p.jpg.html)
(http://i23.photobucket.com/albums/b383/kwm488/20140924_132931_zpshya621lk.jpg) (http://s23.photobucket.com/user/kwm488/media/20140924_132931_zpshya621lk.jpg.html)
(http://i23.photobucket.com/albums/b383/kwm488/20140924_225002_zpswbntvujl.jpg) (http://s23.photobucket.com/user/kwm488/media/20140924_225002_zpswbntvujl.jpg.html)
and i need help. i confirm my amp have noise problem. it is not normal. when i turn on the amp. all volume to zero. but my amp have little 60hz hum. do anyone can teach me where can i start to fix it?
please help
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hi
i do a lot of test and research , i think the brilliant channel hum is normal.
but i have big problem now, the EL84 tube are super hot. and i do research, some user point this out too.
my vox ac30 PT can switch to 240v (here is 220v). will this help to lower the B+. or i need to change the 47R bias resistor to 68R or 82R?
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my vox ac30 PT can switch to 240v (here is 220v). will this help to lower the B+.
It should. Flip the switch and see if it's enough reduction.
or i need to change the 47R bias resistor to 68R or 82R?
That's an option too. It won't lower the B+ but it will allow the tubes to run cooler.
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Hi
Btw, i really don't know how the people use ac30 in the past.
I install new gold lion el84 today. I used the amp 2 hrs. The tube is dead.
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Try with 6p14p-EV or 6p14p-K
http://www.tubes.ru/techinfo/HiFiAudio/6p14pev.html (http://www.tubes.ru/techinfo/HiFiAudio/6p14pev.html)
they are a strongher version of el84 tubes
K
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hi
i measure the voltage today. the EL84 plate is 339v. and the bias is 10.64v.
but i find out the one important thing. the 47R bias resistor. it is very hot even i turn on the amp 1 and 2 minutes. i used 10w resistor here. i measure the ohm. it is increase to 89R when this resistor is hot. i believe this resistor will over heat if i turn on the amp about 1 or 2 hrs.
now, i changed it to 20w resistor.
will my new EL84 tube dead (red plate) very fast because of this bias resistor?
thanks
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47R was a very early value, it will be better if you swap to 68R or 82R
K
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Hi
I used 220v tap before. Heater is 6.6v.
I use 240v tap now.
heater is 6.1v
plate 309v
bias 9.35v
I may change to 230v.
Btw, some people say 82ohm is early version. And i will use 230 or 240 tap. Should i still need to change 47r to 82r bias resistor?
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10.64v across a 47Ω resistor will dissipate 2.4 watts. You're 10 watt resistor will be fine. They are supposed to get hot. Just give it plenty of air circulation around it, ie, don't mount it flat on a pcb.
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You are right about the value of the resistor the oldest schematic I've seen (1960) say 50R the 47R version was on a 1978 amp
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on the CC2 there are two resistors one is 82R and is paralleled with a 150R via the HOT/WARM switch
82R is considered Warm - 50R (82R || 150R) is considered Hot
on the CC2 the bias voltage is 11v with 50R and 13v with 82R -- B+ on CC2 vary from 321v to 324v
K
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Hi
I think i will use 230v tap.
may increase bias don't need to use match el84? Whatbenefits if i use separate bias resistor for each tubenefits if i use seperateistor value.
I see weber ac30 schematic. Plate voltage is 320v.
And vintage ac30 schematic, plate voltage is 320v too(but it mark down it is measure by vintage multimeter, modern multmeter should 5% higher)
But the main problem i have, the 10w bias resistor super hot when i run the amp few minutes. I guess this resistor lost the function when super heat. So it kill my el84. Ac30 Layout request me to use 12w resistor here, but i use 10w. 10w not enough?
Last, i am newbie of ac30 style bias. Is it mean i dont need to use match el84? What benefits if i use separate biss resistor for each tube?
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But the main problem i have, the 10w bias resistor super hot when i run the amp few minutes. I guess this resistor lost the function when super heat. So it kill my el84. Ac30 Layout request me to use 12w resistor here, but i use 10w. 10w not enough?
10.64v across a 47Ω resistor will dissipate 2.4 watts. You're 10 watt resistor will be fine.
Pay attention!
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But the main problem i have, the 10w bias resistor super hot when i run the amp few minutes. I guess this resistor lost the function when super heat. So it kill my el84. Ac30 Layout request me to use 12w resistor here, but i use 10w. 10w not enough?
10.64v across a 47Ω resistor will dissipate 2.4 watts. You're 10 watt resistor will be fine.
Pay attention!
I am confuse, if 2.4w dissipate only. When that resistor will very hot. I can't use my hand to touch it. Is something wrong?
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I am confuse, if 2.4w dissipate only. When that resistor will very hot. I can't use my hand to touch it. Is something wrong?
I used your numbers. But a 10 watt resistor that's dissipating 2.4 watts will put a blister on you finger,
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Is "will put a blister on you finger" mean this resistor should very hot, it is normal? i apologize for my bad english
Btw, i suspect the 250uf 25v (tested is 325uf, it is normal for vintage erie caps) capacitor have problem, maybe leak. (It parallel with bias resistor)But my friend tell me will not. If leak, the resistor should not heat. Current will flow to cap mainly.
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Is "will put a blister on you finger" mean this resistor should very hot, it is normal? i apologize for my bad english
I understand your English. Do you understand mine?
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I understand now. I asked my friend.
So 10w resistor dissipate 2.4w, it will very hot normally.
Just dissipate 2.4w, so it will very hot?
Anyways, i try 20w resistor now.
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HI
i spent whole day to fix my ac30 today.
i did follow
1. add shield cable to PI tube grid pin.
2. try another wire for cut control.
3. changed PI capacitor
4. changed 47ohm bias resistor to 100ohm
5. add shield wire for brilliant pot to top boost tube pin2
6. try to increase main filter cap from 16+16uf to 32+32uf
7. try to change all filter cap.
but all don't help. how should i do ?
i just want to fix (if i turn the brilliant vol pot over 2:00 or 3:00, will have hum). i think it is 50hz hum.
i try to pull PI tube. so it is no hum even i turn brilliant vol pot to max. and i pull top boost tube. it is also no hum even i turn brilliant vol pot to max. when i try to pull other preamp tube. all have hum .
(http://i23.photobucket.com/albums/b383/kwm488/20141118_224059_zps4nirwnjz.jpg) (http://s23.photobucket.com/user/kwm488/media/20141118_224059_zps4nirwnjz.jpg.html)
(http://i23.photobucket.com/albums/b383/kwm488/20141118_224104_zps9lnc6ez9.jpg) (http://s23.photobucket.com/user/kwm488/media/20141118_224104_zps9lnc6ez9.jpg.html)
(http://i23.photobucket.com/albums/b383/kwm488/20141118_224107_zpscsiffqyi.jpg) (http://s23.photobucket.com/user/kwm488/media/20141118_224107_zpscsiffqyi.jpg.html)