Hi All,
I have an old (early 90's) audio innovations series 300 amp that uses 12AU7/12AX7/ECL86 tubes and delivers about 10WPC P/P.
Over the past number of months, there has been an odd noise from the left channel - kind of a rustling, rumbling noise that usually goes away after the amp has been on for 15-20 mins. However, today its been on for an hour and the noise is still there. I love this amp, so want to keep it in good order and original too.
This is meant to be the schematic, but I haven't traced it yet to make sure.
What would the noise be? i take it that there will be capacitors that may need replacing, but which ones should I be looking at first - the 400V/470nF ones?
Any help would be greatly appreciated,
Fran
I have an old (early 90's) audio innovations series 300 amp that uses 12AU7/12AX7/ECL86 tubes and delivers about 10WPC P/P.
Over the past number of months, there has been an odd noise from the left channel - kind of a rustling, rumbling noise that usually goes away after the amp has been on for 15-20 mins. However, today its been on for an hour and the noise is still there. I love this amp, so want to keep it in good order and original too.
This is meant to be the schematic, but I haven't traced it yet to make sure.
What would the noise be? i take it that there will be capacitors that may need replacing, but which ones should I be looking at first - the 400V/470nF ones?
Any help would be greatly appreciated,
Fran
Film capacitors don't typically generate these or any kind of noises, typically failing/old carbon resistors, bad socket contacts, and tubes do.
Sometimes an electrolytic cathode capacitor if drying out may generate some noise as well.
A badly oxidized pot wiper can generate noise, particularly if there is grid current flowing through it. If fitted is the volume pot at all scratchy with or without music playing?
I would suspect tube, socket, and passive parts in that order. (From easiest to hardest)
Sometimes an electrolytic cathode capacitor if drying out may generate some noise as well.
A badly oxidized pot wiper can generate noise, particularly if there is grid current flowing through it. If fitted is the volume pot at all scratchy with or without music playing?
I would suspect tube, socket, and passive parts in that order. (From easiest to hardest)
OK,
well I'll open her up later tonight and clean the sockets/cold joints. I have a spare set of tubes that I can try too. I'll look and see what there is in the line of electrolytics, but not much IIRC.
For checking the resistors: If I do a visual exam, would I just look for signs of burning/heating? or is there some other sign I should watch out for?
Thanks for the hep so far guys...
Fran
well I'll open her up later tonight and clean the sockets/cold joints. I have a spare set of tubes that I can try too. I'll look and see what there is in the line of electrolytics, but not much IIRC.
For checking the resistors: If I do a visual exam, would I just look for signs of burning/heating? or is there some other sign I should watch out for?
Thanks for the hep so far guys...
Fran
OK,
I took out the valves and sprayed in some contact cleaner into the sockets and reinserted and took out and then reinserted the valves again. Problem seems to have more or less gone away now, so I didn't go any further in taking out the PCB and looking for cold joints. None of the components on the PCB look obviously bad, so maybe the problem doesn't lie there.
The small signal valves (12AX and AU7) are relatively new - EI brand ones. The ECl86s are original TFKs, and I have a set of Mullards as well.
So I can probably try these too.
Anyway I'm going to let the amp cool, do the sockets again, maybe clean the pins and have a look to see if any of the sockets seemto have bigger gaps in the pins.
Thanks so much for the help so far,
Fran
I took out the valves and sprayed in some contact cleaner into the sockets and reinserted and took out and then reinserted the valves again. Problem seems to have more or less gone away now, so I didn't go any further in taking out the PCB and looking for cold joints. None of the components on the PCB look obviously bad, so maybe the problem doesn't lie there.
The small signal valves (12AX and AU7) are relatively new - EI brand ones. The ECl86s are original TFKs, and I have a set of Mullards as well.
So I can probably try these too.
Anyway I'm going to let the amp cool, do the sockets again, maybe clean the pins and have a look to see if any of the sockets seemto have bigger gaps in the pins.
Thanks so much for the help so far,
Fran
Amp seems quiet now. I took out the valves again and cleaned the pins with a bit of 1200 grit (they were actually quite dirty although they aren't in that long <1 yr). Sprayed in another bit of contact cleaner and reassembled. So far it seems OK, but really I'll only know over time.
So hopefully I won't need to post in this thread again !!!!!!!!!
thanks again to all who helped, excellent diagnosis Doctors....
Fran
So hopefully I won't need to post in this thread again !!!!!!!!!
thanks again to all who helped, excellent diagnosis Doctors....
Fran
The fact that the pins were quite dirty might suggest some arking over. This manifests itself exactly as the sound you describe. It may prove necissary to improve the grip on the valve socket.
I have had similar issues after to many adjustments and modification to the components attached to the sockets.
Shoog
I have had similar issues after to many adjustments and modification to the components attached to the sockets.
Shoog
The pins on the ECL86s were just dirty looking, but the ones on the 12AX/AU7s were actually a bit "blue" looking - you know how metal looks when it gets a bit hot. Now a light sandpapering removed it (1200 grit and only really a quick rub) so its not like any serious heat got them.
In any case, I've had it on for most of today and not a single noise out of it, so it looks like that was the issue.
Hey Shoog, whereabouts are you, Irish DIYers seem in short supply, only myself yourself and john kenny! (and I don't know if I even qualify).
Fran
In any case, I've had it on for most of today and not a single noise out of it, so it looks like that was the issue.
Hey Shoog, whereabouts are you, Irish DIYers seem in short supply, only myself yourself and john kenny! (and I don't know if I even qualify).
Fran
I'am from England originally though my family is Irish. We're based out in the North of Roscommon near Boyle. I have spoken to John Kenny and he seems to have the same thinking as me. I have a local neighbour who's into radio, but has a side interest in Audio. We're going to do a speaker project together and then he's thinking about a valve amp as well.
Where are you. Distances aren't so huge that it wouldn't be possible to have an Irish meet (of three).
Shoog
Where are you. Distances aren't so huge that it wouldn't be possible to have an Irish meet (of three).
Shoog
The original ECL86 based "Baby Huey" was brought back to me last week with just such a symptom in one channel. I found I could make it come and go by wiggling one ECL86 in its socket. Thorough clean of the tube pins and a spray of the socket with Contact Cleaner fixed the problem.
Cheers,
Ian
Cheers,
Ian
Hey Guys,
Don't go ahead without me - would love to meet up. I will be travelling down to Portlaoise around the end of the month & would love to get together then in Kildare. I could bring along Sonic t-amp (and your one too Fran), SKA 150W SS amp Baby Huey rebuild of Rogers Cadet III tube amp along with Rogers LS3/5a speakers.
Hey Fran, I just saw some of your postings on Cloney's forum - I see that you have some Maggies - would like to hear & test out my amps with them.
Shoog, I would love to hear your latest tube amp.
Let's organise this off air
John
Don't go ahead without me - would love to meet up. I will be travelling down to Portlaoise around the end of the month & would love to get together then in Kildare. I could bring along Sonic t-amp (and your one too Fran), SKA 150W SS amp Baby Huey rebuild of Rogers Cadet III tube amp along with Rogers LS3/5a speakers.
Hey Fran, I just saw some of your postings on Cloney's forum - I see that you have some Maggies - would like to hear & test out my amps with them.
Shoog, I would love to hear your latest tube amp.
Let's organise this off air
John
I could bring along my Zen V3. My buffered gainclones (OPA527and transistor). My choke loaded parafeed RH807 and my latest 6AS7 interstage transformer amp. Hopefully I might have my Buschorns up and running again. Also My two valve preamps - one based on a CCS loaded 5687 and one based on the Vacuum state FVP5.
Could be a long day.
Shoog
Could be a long day.
Shoog
Oooh,
Sounds even more interesting. Now all we need is a date & a place. How does end of month sound to all? Where to meet.
Fran, would any of the cloney forum members be interested in hearing DIY & bringing some commercial gear to hear?
Correction - I think Fran has Quad ESL's & not Maggies as I said.
John
Sounds even more interesting. Now all we need is a date & a place. How does end of month sound to all? Where to meet.
Fran, would any of the cloney forum members be interested in hearing DIY & bringing some commercial gear to hear?
Correction - I think Fran has Quad ESL's & not Maggies as I said.
John
Hey Ian,
Good to hear the original ECL86 Baby Huey is still being enjoyed. Mine is still working although I have tried triode strapping it (no UL OPT) with 150R to plate - not much difference in sound - even the loudness didn't reduce. I wonder did I do something wrong?
Also about to try CCS cathode biasing with LM317 (I know not the best CCS around but should give me an idea of how it might sound).
Still never got my GNF working - did try to tap it off the 8 ohm tap (instaed of 16 ohm secondary tap) & it now distorts on any slightly louder sound - is this clipping? Maybe this is as a result of the triode strapping.
Anyway, want to get it in good shape for the planned listening session mentioned here, so any advice welcome.
John
Good to hear the original ECL86 Baby Huey is still being enjoyed. Mine is still working although I have tried triode strapping it (no UL OPT) with 150R to plate - not much difference in sound - even the loudness didn't reduce. I wonder did I do something wrong?
Also about to try CCS cathode biasing with LM317 (I know not the best CCS around but should give me an idea of how it might sound).
Still never got my GNF working - did try to tap it off the 8 ohm tap (instaed of 16 ohm secondary tap) & it now distorts on any slightly louder sound - is this clipping? Maybe this is as a result of the triode strapping.
Anyway, want to get it in good shape for the planned listening session mentioned here, so any advice welcome.
John
I might be able to arrange a free gaff here towards teh end of the month. Don't know when exactly yet, would need to ship off the wife and kids for the afternoon. Maybe if everyone would email me and we can move this discussion off-line?
I should have my passive pre back up by then and I have just finished a Teres type turntable - have a look at the teres 340 on the teres website. I have a home brew record washer too.
email is francis dot morrin
AT
gmail
dot
com
Fran
I should have my passive pre back up by then and I have just finished a Teres type turntable - have a look at the teres 340 on the teres website. I have a home brew record washer too.
email is francis dot morrin
AT
gmail
dot
com
Fran
John,
Your probably only getting somewhere between 5-6watts before clipping. From what you say about your speakers thats just not enough. I would advise going back to pentode or UL. From my slight understanding of the Baby Huey it uses plate to plate feedback. I found that with my RH807 the plate to plate feedback made the sound of the triode and pentode nearly identical.
Shoog
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