| Author | Message | ||
     Neil C |
I read last week on the internet that healthy tubes either don't glow or they glow blue. If they glow pink/red apparently they are worn out, are likely to fail and need to be replaced. I had a look at my Spacexpander tubes and 2 of them were glowing pinkish/red! So I decided to replace all 3. I fitted them yesterday and hey presto, my hum problem which I thought was probably internal has dissapeared! And also the sound is improved, there seems to be a bit more power going through the spring tank and the sound we are after from a Spacexpander was more apparent. I got my tubes/valves on-line from Watford Valves (UK). They have a good site. http://www.watfordvalves.com/aboutus.htm | ||
| Neil C |
Sorry, that link doesn't work properly, this one should: http://www.watfordvalves.com/mainindex.htm | ||
| interruptor |
good to know! mine glow reddish too.. what about your new tubes what's the color like? | ||
| Neil C |
My new ones don't glow at all, which would make sense according to the principles described below. If all 3 had been glowing pink I wouldn't have been so confident, I'm not totally sure about the info below, but because only 2 were it seemed good evidence something was wrong. The thing I read is from a UK distributor of Accutronics tanks, although the site doesn't seem to have been updated for a while: 'Blue glow This is caused by ionisation of gas molecules when the vacuum is very soft. In extreme cases, the glow might be the pink/violet described below. Pink/violet This is normally caused by a crack in the glass envelope. Valves exhibiting this are usually ready to fail and should not be used. Thermionic emission is the process by which the electrons are produced for the current that will flow in the valve. In a solid metal, the atoms are held in a crystal lattice. Most electrons are strongly bound to their atoms, but some are free to move through the it. It is these that are used for conduction. At room temperature, the free electrons are constrained to the crystal lattice. If they are provided with more energy, they can leave the surface of the crystal in process similar to boiling. In a valve, this extra energy comes from the heater. The boiled off electrons will remain close to the metal, because it now has a net positive charge. These electrons form a cloud around the metal called a space charge. The heaters of a valve can be operated at +/- 10% of the rated voltage. If the voltage is too high, then the oxide coating of the cathode will eventually start to evaporate. If this happens it is often deposited on the grid. Evidence that this has happened is an increased grid leakage current. Operation at lower voltages is less risky. With a lower voltage, there is a reduced space charge. As long as the anode current is not sufficient to exhaust the space charge then no damage will occur. If the space charge is regularly exhausted, the cathode is robbed of its protection and the oxide coating is burned off.' | ||
| Khenu |
Hi, I just picked up a spacexpander as well. How can I tell if the valves are good or not? Which replacement valves should I get? How do I safely remove the metal encasing around the valves? Thanks for any advice. Peace, Khenu www.rootsandwires.com | ||
| Neil C |
Basically, blue or no glow they are OK. Red or pink glow they are not. It can be a little tricky to tell if any light you see is glow from the tube or a reflection from your room lighting. Make sure its glow (if looking bad) from the tube before you rush and buy new ones. Or if you think your Spacexpander is not functioning well, then I guess changing the tubes is worth a try. The metal casings around the tubes just come off - gently force them sideways and they'll lift off - they are held on like a plastic lid on a container. They will go back on easily. At least this is true on mine. The big casing (not a tube to be replaced) at the end does not come off. The tubes just pull out and you can push new ones in - no technical expertise is required. I can recommend Watford valves which I gave a link to above. They deliver internationally. The 12ax7 are about £5 each and the 7247 I think was about £8. You'll be amazed at the variety of tubes - I went for the Russian Electric Harmonix 12ax7's. The person at Watford valves replied quickly to a question I emailed - try him if you have any queries. | ||
| Khenu |
Hi Neil, Thanks for the response. If one of the tubes was blown, would it totally eliminate the reverb effect? I bought mine off e-bay and the first tube (farthest from the large casing) seems blown. There is a bit of white frost at one end, and it seems like a hairline crack on the side. Sound seems to go through, but there is no reverb effect at all. Even when I shake the springs, no modulation. They tell me that it was working fine before it was sent, so perhaps the tube cracked on transit. Perhaps it never worked. I'm debating whether I should try replacing the tube or if I just need to return it. Fortunately, they're willing to take it back, as I bought it from a music store via E-bay. I would love to hear any thoughts! Also, do any of you all have special ways in which you've mounted your spacexpander? I would love to see some pictures and ideas if so! Thanks, Khenu | ||
| Neil C |
I have no electronic expertise, but I would guess that the missing tube might be responsible for no reverb. I really don't know though. Apparently the elctronics inside the thing are simple, and any good audio electronics person should be able to repair it (if the problem is more than the tube). I posted before ,on here, some info that Hugh Robjohns of Sound on Sound magazine gave me - its worth finding and reading. I saw an electronics diagram of the Spacexpander (someone linked me to it on the SOS forum) once- if I can find it again I'll point you to it. I just have my spring tank loose (in the recommended vertical position). I might take a picture and post where I have the rest of it. | ||
| Neil C |
Here is the link to the schematic: http://www.triodeel.com/k10.gif | ||
| interruptor |
no need to go offsite, here is the schematic and parts list in the original user manual.  the 2 schematics look different. probably they are electrically equivalent.  in case you want to know what Mr. Avery Fisher looked like, look here! | ||
| Triffidd |
Khenu, you wrote: "If one of the tubes was blown, would it totally eliminate the reverb effect? I bought mine off e-bay and the first tube (farthest from the large casing) seems blown. There is a bit of white frost at one end, and it seems like a hairline crack on the side. Sound seems to go through, but there is no reverb effect at all. Even when I shake the springs, no modulation. They tell me that it was working fine before it was sent, so perhaps the tube cracked on transit. Perhaps it never worked. I'm debating whether I should try replacing the tube or if I just need to return it. Fortunately, they're willing to take it back, as I bought it from a music store via E-bay. I would love to hear any thoughts! Also, do any of you all have special ways in which you've mounted your spacexpander? I would love to see some pictures and ideas if so! " I seem fated to have to tell you for the 2nd time that you seem to have all the gear and NO IDEA! You bought a Spacexpander probably because you thought it was the cool thing to have, because the dub guys used to use it in the 70s. Never mind that you don't actually produce dub yourself.. weird logic you got there. Anyway this is not a personal attack. I just want to say that you ought to know already that when a tube is frosted it's f*cked, to use the technical term. When it's cracked, it's downright dangerous to use. You have to replace it. Oh what the heck, you can always go back to using commercial breakbeat loops, hey? | ||
| Neil C |
Khenu- Perhaps I should have pointed out too that the tube is obviously broken - I didn't realise at first you might have any doubt about that. The tube is obviously there for a reason and even if there is something else wrong then you need to replace it. I wouldn't want to turn on a piece of electronics where there was a component missing -it could be dangerous to you and the equipment. Anyhow in this now rather mixed thread I'm going to show you my Spacexpander (the spring tank is darkly visible in the bottom right). The control knob is secured on with several layers of sticky tape:  | ||
| Neil C |
And my high rise studio:  And my monitor system:  | ||
| Khenu |
Neil, Thanks for your response. It's nice to see those images of your studio. This is my first foray into working with something tube-powered, so excuse my ignorance. I'm just trying to weigh things financially to see if all the repairs are worth it. I didn't know if the obviously broken tube would be the sole cause of the problem I was having. Anyway, I replaced the tube and the reverb is in fact now working. Now's there's just a pretty nasty hum. Do you think that by replacing the other tubes, which seem to be the original Fisher ones, the hum might go away? I know from one of your posts that you dealt with some hum as well. My hum only comes when I turn the potentiometer on - it gradually increases as I add more reverb. I have an option of returning this unit by mail, and it would cost me $30-40 to replace the other tubes just to see if it makes a difference, so I don't want to try if it doesn't have a high chance of working. On the other end, it would be nice to use a real spring reverb, versus vst's, on the dubwise tracks I am working on. I know that the sound and sound guy had recommended that you change the capacitors, so if that's what I might need to do, it would probably be worth it for me to return it. Thanks again for your responses. Sincerely, Khenu www.rootsandwires.com | ||
| Triffidd |
Khenu it's remarkable comparing the contrast between your verbose pomposity and your apparent confusion over what to do with a cracked valve... Just answer this question for me: do you still maintain that you produce reggae? The verbose and pompous pretentious drivel on your website does nothing to detract from the truth that you have no musical talent whatsoever, and that the saddest thing of all is that you're nowhere near as clever as you think you are and as you keep trying to pretend. Just about everyone else can produce better music than you. Why don't you give me a link to another half-hour of commercial breakbeat crap. I could do with a laugh.. | ||
| Neil C |
Steady on Triffid. I like the Roots and Wires site. I think its a sort of take it or leave it thing. If you don't like it you don't like it, but its really a matter of personal opinion. I'm enjoying 'special agent k meets vishal nagar' as I type. Khenu - the tubes. My hum was solved by replacing all the tubes. Its no surprise that tubes that are possibly 40 years old won't be working as new. Even if all new tubes don't solve the problem you'll at least have a set of all new tubes that you can fit in to a repaired unit. Here is the other info I posted that might be useful to a repairer: http://www.interruptor.ch/cgi-bin/discus/messages/1/850.html?1100695624 | ||
| Triffidd |
You're right Neil. It is a take it or leave it sort of thing. I just find his music so offensive I sort of lose control when addressing him. I think it's because Khenu and I would use exactly the same words to describe dub and even claim the same influences (e.g. Lee Scratch Perry), but when it comes down to production I stretch the limits of my abilities to come up with raw, authentic DUB REGGAE MUSIC, but Khenu would cut and paste loops and claim honours. It drives me mad. Like, snip a bit of LSP, a recording of someone tapping out a nonsense beat on a table (does he even know what a one-drop is?) and a commercial breakbeat loop, and claim you have a reggae sound?? Like, WTF? Anyway, I'll shut up now because I'm going off on one again. | ||
| satan4mmm |
Kansst du mir ein Speisekarte zeigen ?mmm | ||
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