Topic: HELP! Having problems with my tube amp

[trod93]

Hi to all!

I bought an EL34 push-pull 35wpc almost 2 months ago from a shop in Park Square which was traded in for a higher model aftr 6 months of usage. I hooked up my hard to drive 87dB AR93 and observed it had trouble driving these speakers. There was a little bit of distortion at only 9-10 o'clock volume level. But, what really troubled me, after 2 days of listening to it, was when one of the output tubes on the left channel glowed like a light bulb followed by a cracking sound from the speaker. I thought it will blow ,so, I turned it off immediately. It happened once again but this time on the right channel. At the back of my mind, it might be the speakers. But, I used to have a 30wpc Rotel which drove these speakers with ease.

I brought the amp to their shop to have it checked. After 3 days, I was told that the on/off switch was intermitently losing contact which affected the circuitry and was replaced. 2 days after, the new switch won't go on "OFF" mode. When you turn "OFF" the unit it goes back to "ON" position, the locking mechanism in it I presume. I brought it directly to the factory for another check up. The switch was replaced then a capacitor was added. I also replaced my ARs with a pair of 91dB B&W floorstanders for good measure. I love the sound coming from the B&Ws and I thought these were a perfect match. Alas, it happened again last night just after 2 weeks of audio bliss. By the way, the "new" switch is back to its old unreliable state, on "ON" position for all eternity a day or two after replacement. I use my avr as the on/off switch ever since.

What could be the problem here? Is it just the switch? It's intermitent in nature, but, hey, it's next to impossible to have your eyes glued on the amp the whole time you're listening. What if you need to piss? It happens very fast.

It's my first dive into tube gear and I'm extra careful but really frustrated at this point. You, the tube gurus, might have a different opinion or the same experience on this matter. Hope you can help a pi**ed off newbie here.

Thanks.

[markmlists]

Hi. Not a tube guru or tube anything but can you post the brand of the gear (and the shop) in question? Sometimes brands have a known design/construction weakness that the other guru's know. Thanks and good luck.

[oweidah]

im not a guru.
i suggest you deal with the shop till all means are exhausted. they made it so i assume theyre qualified to fix whatever problem encounterd. you may request for a unit change if its stated in their warranty or if they are amenable to that arrangement. why not try it?

[qguy]

Glowing like a light bulb... Thermal runaway...

Hard to drive at 87DB...not exactly as I have had 86 DB "insensitive" speakers and a PP el34 can drive it to ear bleeding levels, a PP El84  (even smaller can drive it to same levels at 15 watts each) w/o any distortion.

There is definitely something wrong with the amp.. they say its the switch.. i doubt the switch is the cause of the problem, it would only kill the power and should not cause the tubes to go to thermal runaway. Unlesss.. grounded siya sa case...but in that case you should have died from electrocution..hehehe

[JojoD818]

First of all, you shouldn't have used the term "tube guru", you're scaring everyone now.  There is no need to tell us the shop or brand of your amp but we are going to need some details to help you out. What are the tube compliments? Is it tube or ss rectified?

Secondly, you should state the type of biasing. Is it fixed bias? Auto bias? If you don't know then checkout the chassis top, back, sides and look for bias adjustment knobs, trimmers, etc that says bias adjust. If you can't find it then it is safe to assume it's an auto bias output topology. But if you want to be sure, then call the shop and ask for details.

A glowing output tube can be signs of a faulty output tube, faulty coupling cap, faulty cathode resistor, and if it's a fixed bias, a faulty negative bias supply can push your outputs to the limits. For all we know, it can even just be a cold solder (I see this a lot).

Frankly, I see no connection regarding the power switch and the glowing tubes. 

And lastly, I understand your situation but please, don't get pi**ed off and lighten up a bit. Only a peaceful mind can solve problems so cheer up. 

[trod93]

Hi jojod818,

Well, if it's your 3rd trip to the service center for the same problem, I guess it's about time to get p...ed. But, don't worry, I'm a lover not a fighter. I was about to name the brand but your reply came in first. Let's keep it at that for the time being. By the way, I'm from Fairview and travelling all the way to the south with a 45 lb amp on your back for the 3rd time is quite hazardous to your health .
 
Anyway, it's a fixed bias design and ss rectified. It's got 4xEL34, 2x12ax7 and 1x6dj8. The output tubes and the 6dj8 are Svetlanas, the 12ax7 are somewhat like JAN, not very readable. I was told the tubes have about 300hrs on them before I got it. The warranty was passed on to me so I kinda expected the unit to be in tip-top shape especially after 2 visits already.

Hope to hear some more comments and advises.

Thanks guys!

[markmlists]

There is no need to tell us the shop or brand of your amp

I should have separated the 2 questions for they serve 2 purposes (one is technical in my v-humble attempt to help and one for entertainment value).  sorry senyor.

[JojoD818]

Hi jojod818,

Well, if it's your 3rd trip to the service center for the same problem, I guess it's about time to get p...ed. But, don't worry, I'm a lover not a fighter. I was about to name the brand but your reply came in first. Let's keep it at that for the time being. By the way, I'm from Fairview and travelling all the way to the south with a 45 lb amp on your back for the 3rd time is quite hazardous to your health .
 
Anyway, it's a fixed bias design and ss rectified. It's got 4xEL34, 2x12ax7 and 1x6dj8. The output tubes and the 6dj8 are Svetlanas, the 12ax7 are somewhat like JAN, not very readable. I was told the tubes have about 300hrs on them before I got it. The warranty was passed on to me so I kinda expected the unit to be in tip-top shape especially after 2 visits already.

Hope to hear some more comments and advises.

Thanks guys!

If it's fixed bias then there should be some adjustment knobs or trimmers to set the bias for the EL34, so do you see it in your amp? This should be set properly so that your amp's output section can work right.

Sometimes the primary culprit is a leaky coupling cap between the output tube and the tube driver since it grabs the negative voltage that sets the output tubes bias. Starving the output tubes negative bias means the output tube will go into full conduction, and then qguy's post will happen.

I should have separated the 2 questions for they serve 2 purposes (one is technical in my v-humble attempt to help and one for entertainment value).  sorry senyor.

Hi,

Listen to Tony, he always say "there is nothing new under the sun". I hate to say it but I agree with him, I find nothing new with the amps that I open (for repair purposes), maybe new combinations of technology but the basic topologies still remains the same.

So what does this mean? It means we don't need to know the brand of the amp to fix it. 

I'm a bit lost with the entertainment part though. 

[iceman90a]

my advise - return it ask for your money back or a new unit

[trod93]

No indicators of knobs, trimmers and the like, just plain allen screws all around the base. I will bring the unit back tomorrow or Monday the latest. They might as well do something about it or I might just take iceman's advise. In that case, JojoD, you got a potential customer here. PM me your contact nos., I will call you one of these days. Earl has high praises on you.

Hope this post ends right here after my next trip to the service center. Will keep you posted. Parang mali yata yon ah?

Thanks again.

[JojoD818]

No indicators of knobs, trimmers and the like, just plain allen screws all around the base. I will bring the unit back tomorrow or Monday the latest. They might as well do something about it or I might just take iceman's advise. In that case, JojoD, you got a potential customer here. PM me your contact nos., I will call you one of these days. Earl has high praises on you.

Hope this post ends right here after my next trip to the service center. Will keep you posted. Parang mali yata yon ah?

Thanks again.

Yikes, so it's not fixed bias but an auto bias, sorry my bad. Same suspects though, but this time cathode resistor and bypass cap included. 

Anyway, I sure hope that they fix the problem for you this time. Besides, if it's still under warranty, being repaired by an unauthorized tech would void your warranty and any hopes of negotiations with them. Try everything before you take iceman's advise. 

Do keep us posted, I hope your next post would be good news.

 

[Jakob]

sir,

have you tried interchanging the output tubes (left/right), the tubes maybe faulty already.

i assume you're using a reliable avr.

what am i talking about, i'm no guru 

just trying to help in any way i can.

 

[arnoldc]

Bakit di mo masabi kung sino yung shop? Phasetron is one that fits your description.

As previously posted, the switch has nothing to do with the problem. It's faulty, obviously. Send it back and get your money back. Pagawa ka na lang kay JojoD.

[trod93]

I was tempted to name the shop but I will let you guys make your assumptions for the time being. If nothing happens after my 3rd visit then maybe I will just do that. Negative feedbacks travel fast and with more impact. I'm sure that'll wake them up and hopefully give their clients the service they deserve.

Really appreciate all your inputs and support.

Thanks again.

[JojoD818]

Bakit di mo masabi kung sino yung shop? Phasetron is one that fits your description.

As previously posted, the switch has nothing to do with the problem. It's faulty, obviously. Send it back and get your money back. Pagawa ka na lang kay JojoD.

Naku baka sabihin may vested interest ako, get it fixed muna - very interested ako dun sa naging problema.

I was tempted to name the shop but I will let you guys make your assumptions for the time being. If nothing happens after my 3rd visit then maybe I will just do that. Negative feedbacks travel fast and with more impact. I'm sure that'll wake them up and hopefully give their clients the service they deserve.

Really appreciate all your inputs and support.

Thanks again.

I was browsing the thread... "How many members of Pinoydvd are into Tubes?". 

[markmlists]

I'm a bit lost with the entertainment part though. 

Entertainment kasi I was tempted to diagnose ala dr. house hehe.

*Patient- Tube amp
*User-Sir trod. he said he is a tube newbie (like me)>Common newbie mistake-crossing + and - speaker wire which kills opt.
*Clues and symptoms-(1) only one side is affected <Glows> (2)cracking/distoring sound at just 9'oclock volume
*Uknown- BRAND of amp. Is it a brand with protection circuit for shorts? If no, differential diagnosis> 1 DEAD OPT.

Entertainment lang, since konti lang alam ko (mapa new or old under the sun).

[JojoD818]

Entertainment kasi I was tempted to diagnose ala dr. house hehe.

*Patient- Tube amp
*User-Sir trod. he said he is a tube newbie (like me)>Common newbie mistake-crossing + and - speaker wire which kills opt.
*Clues and symptoms-(1) only one side is affected <Glows> (2)cracking/distoring sound at just 9'oclock volume
*Uknown- BRAND of amp. Is it a brand with protection circuit for shorts? If no, differential diagnosis> 1 DEAD OPT.

Entertainment lang, since konti lang alam ko (mapa new or old under the sun).

Excellent diagnostic lists, markmlists (kinda rhymes huh?  ).

Read trod93's first post carefully, especially that sentence pertaining to "audio bliss" and it will clear things up for your list.

Did you know that all tubeamps (at least the ones that I know of) in the market (be it PP or SET) don't have any active output short circuit protection? Now add that up to your "I know" list, marmlists (it really rhymes).

[arnoldc]

bakit nawala si trod93? 

[oweidah]

bakit nawala si trod93? 

yeah bakit nga ba?

I was tempted to name the shop but I will let you guys make your assumptions for the time being. If nothing happens after my 3rd visit then maybe I will just do that. Negative feedbacks travel fast and with more impact. I'm sure that'll wake them up and hopefully give their clients the service they deserve.

Really appreciate all your inputs and support.

Thanks again.

sir trod93,
i believe, you should update your post for the sake of other members who might have shelved plans to buy from that shop due to the negative feedbacks. its kinda unfair for the shop to have a negativ rep esp. at this time (xmas bonus season) now if your problem has not been resolved, the more you should update. i hope alls well that ends well with you and the shop.

[newbie pa rin]

Yes sir kindly update your post.
Im looking into tubes pa naman sana, natakot tuloy ako.
Sa Phasetron pa naman sana ako bibili.

[JojoD818]

I believe he's in the process of bringing his amp back for repairs pa, mainipin pala kayo.

[RU9]

Just to balance things out, I am a customer of Phasetron and  never experienced any problems. Even browsing the AMX thread, all Phasetrons customers seems satisfied with their gears.

Since Trod93 never mentioned the name of the shop, he might be referring to a different shop.

[oweidah]

Just to balance things out, I am a customer of Phasetron and  never experienced any problems. Even browsing the AMX thread, all Phasetrons customers seems satisfied with their gears.

Since Trod93 never mentioned the name of the shop, he might be referring to a different shop.

yeah i hope so.
but pls check his post. ilan ba ang audio shops at parksquare (1&2) na nagbebenta ng el34amp at ilang ang may factory? tnx

Hi to all!

I bought an EL34 push-pull 35wpc almost 2 months ago from a shop in Park Square which was traded in for a higher model aftr 6 months of usage. I hooked up my hard to drive 87dB AR93 and observed it had trouble driving these speakers. There was a little bit of distortion at only 9-10 o'clock volume level. But, what really troubled me, after 2 days of listening to it, was when one of the output tubes on the left channel glowed like a light bulb followed by a cracking sound from the speaker. I thought it will blow ,so, I turned it off immediately. It happened once again but this time on the right channel. At the back of my mind, it might be the speakers. But, I used to have a 30wpc Rotel which drove these speakers with ease.

I brought the amp to their shop to have it checked. After 3 days, I was told that the on/off switch was intermitently losing contact which affected the circuitry and was replaced. 2 days after, the new switch won't go on "OFF" mode. When you turn "OFF" the unit it goes back to "ON" position, the locking mechanism in it I presume. I brought it directly to the factory for another check up. The switch was replaced then a capacitor was added. I also replaced my ARs with a pair of 91dB B&W floorstanders for good measure. I love the sound coming from the B&Ws and I thought these were a perfect match. Alas, it happened again last night just after 2 weeks of audio bliss. By the way, the "new" switch is back to its old unreliable state, on "ON" position for all eternity a day or two after replacement. I use my avr as the on/off switch ever since.

What could be the problem here? Is it just the switch? It's intermitent in nature, but, hey, it's next to impossible to have your eyes glued on the amp the whole time you're listening. What if you need to piss? It happens very fast.

It's my first dive into tube gear and I'm extra careful but really frustrated at this point. You, the tube gurus, might have a different opinion or the same experience on this matter. Hope you can help a pi**ed off newbie here.

Thanks.

[gobledgeek]

Sa pagkakaalam ko umaabot na na malapit sa 5,000 post at 55,000 views iyon AMX na thread, ni isa wala akong nakitang matinding complaints sa mga AMX product. Kung meron di na pinopost siguro dahil minor at nasosolusyunan.
Hanggang hindi sinsabi ni trod93 yun pangalan ng shop, we should not try to add damaging comment 'coz hearsay lang whatever we say o speculation lang dahil kwentuhan.
Anyway, sinabi rin naman ni trodt93 na pangalawang owner na siya na pinasahan ng warranty lang, lahat naman ng bagay pwede masira depende sa use and abuse pero meron din naman isolated cases na me mahinang piyesa at bumibigay na subject naman sa warranty.

[oweidah]

Sa pagkakaalam ko umaabot na na malapit sa 5,000 post at 55,000 views iyon , ni isa wala akong nakitang matinding complaints sa mga AMX product. Kung meron di na pinopost siguro dahil minor at nasosolusyunan.
Hanggang hindi sinsabi ni trod93 yun pangalan ng shop, we should not try to add damaging comment 'coz hearsay lang whatever we say o speculation lang dahil kwentuhan.

hindi nga sinabi ni trod93 eh iilan ba ang audio shops sa parksquare (1&2)at ilan ang may factory? sino ba ang tinatamaan at naapektuhan? instead makabenta ngayong kapaskuhan /bonus time....look at newbie pa rin post... 

Yes sir kindly update your post.
Im looking into tubes pa naman sana, natakot tuloy ako.
Sa Phasetron pa naman sana ako bibili.

btw disclaimer - hindi po ako spokesman ng AMX phasetron.
 

[ianmorales]

Bro, Any update with your Amp?

[trod93]

Hi to all!

I never thought there would be this much interest with my tube amp. Anyway, to update you guys, I brought it back to the shop last Saturday, unfortunately, the owner and the tech are out. I called this afternoon and I was told that, after the owner read the complaint form w/out checking the unit, the tubes need to be changed at my expense.  ???Wow! I told the staff that I have to talk to the owner directly because I feel he doesn't exactly know what's really wrong with the amp. I don't think there is a need to change the tubes at this point because when it's operating normally, it sounds very good, although, there is 1 tube that has a slight reddish glow na(sign of weakness). This is the first tube that glowed and made a loud cracking sound on my left speaker. It caused a tear on the midrange driver surround.

Sold my other amps for this lemon. No music for the last 3 days >:(What a life !Can't appreciate the sound from mini compos naman. Gusto ko ng patulan yung NAD 304 ni kudoz para lang matanggal yung kati. Sir kudoz pwede ba sa 4k na lang?

I will call again tomorrow and hopefully get to talk to him na.

Abangan ang susunod na kabanata.

[oweidah]

Hi to all!

I never thought there would be this much interest with my tube amp. Anyway, to update you guys, I brought it back to the shop last Saturday, unfortunately, the owner and the tech are out. I called this afternoon and I was told that, after the owner read the complaint form w/out checking the unit, the tubes need to be changed at my expense.  ???Wow! I told the staff that I have to talk to the owner directly because I feel he doesn't exactly know what's really wrong with the amp. I don't think there is a need to change the tubes at this point because when it's operating normally, it sounds very good, although, there is 1 tube that has a slight reddish glow na(sign of weakness). This is the first tube that glowed and made a loud cracking sound on my left speaker. It caused a tear on the midrange driver surround.

Sold my other amps for this lemon. No music for the last 3 days >:(What a life !Can't appreciate the sound from mini compos naman. Gusto ko ng patulan yung NAD 304 ni kudoz para lang matanggal yung kati. Sir kudoz pwede ba sa 4k na lang?

I will call again tomorrow and hopefully get to talk to him na.

Abangan ang susunod na kabanata.

trod93, tnx for the update. sir i think more at issue here that people await is how that shop handles your problem. now with your side aired at least half of the complete picture is presented and the ball is on the other court. still hoping for the best resolution to your case.

[JojoD818]

trod93,

what brand are your EL34s? approximately, how many thousands of hours has it run (at least on your end since you got it as a traded amp)?

to be honest, pati ako naiinip na din sa ending. 

[trod93]

I finally got to talk to the tech. I told him again what I'm experiencing with the amp. He mentioned something like "baka sobrang boltahe". I told him that whatever it is he should take a look and check, Saturday pa yung amp ko dun. He will check it out daw after finishing his work on another unit. If they only know this thread and that it has been read almost 500 times na maybe they'll take more interest on it just like you guys. I'm sure they know it's them that I'm mentioning here. The second time I brought the amp there sabi nila "Eto na naman". Kilala na nila amp ko dun eh.

The day I got this amp to this day I would say I have around 50hrs max on it, so, if you add 300hrs from the past owner that'd be 350hrs. Recently kasi I haven't been using it that long, 1 hr lang pagod na ako kakatitig sa kanya. Or, 30mins pa lang naka-glow na tubes. Sometimes my friends would come along and alangan akong buksan baka mapahiya ako. It's not a comfortable or relaxing experience anymore.

I guess I should mention audioamplified na rin. He pmed me and was offering to replace the unit without any questions if it's theirs. What a nice gesture di ba. He did it discretely and fast, I guess after only 3 responses from other members, without letting the other members know it. Buy Cayin if you have the budget, I'm sure you'll be taken care of.

Will check status again tomorrow.

Thanks.