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Fisher Space Expander Restoration Checklist (please help me)

 
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stranded horse



Joined: 07 Mar 2011
Posts: 65

PostPosted: Thu Mar 10, 2011 5:40 pm    Post subject: Fisher Space Expander Restoration Checklist (please help me) Reply with quote

Hello,
I've been reading this forum for ages, it's a very valuable source of knowledge, but I only recently registered to this forum, because I aquired an old Spaceexpander really cheap. Needless to say it is trashed, so I will need to put a lot work into it. My skills with the soldering iron are ok, my electrics skills are only medium though, so I could need some help, and I hope together we can help many people who read this to restore the Fisher Spaceex
I thought this would also be an opportunity to have one thread to gather all information needed to restore a Spaceexpander, because I would guess many Spaceexpanders surfacing could be in a state not dissimilar to mine.
Mine is missing the control knob, the reverb tank and the tubes, and also some of the caps are obviously broken




1) get the schematic & parts list



2) replace all the capacitors (now the parts list is really handy when you go shopping for these parts)

If the caps are all original, they are almost 60 years old and pretty much bound to be broken. There is no way of testing a cap with a regular multimeter that I know of, so if you checked everything else, and your Spaceex is still not running, be prepared to replace every single one of them. Besides capacitors are not pricey, and none of them should cost you more than a couple of cents with the exception of the big 4 section elco (the big one sticking out of the case). If you found a replacement it would probably cost between 10 and 20 bucks (I judged this on the price of commonly available Mallory 4 Section Eletrolytics)

Question: has anyone found a direct replacement for the 4 section cap? In the parts list it says 1000V, but theoretically a 350V one would be enough, right?



3) replace tubes if necessary

Luckily the tubes used are still being made and readily available. Specially the 12ax7 is still being produced in large quantities and the cheap ones made by Sovtek (approximately 8 Euros) should do the job.
For the 7247 there is less choice, and they are a little bit more expensive (the ones I found sell at around 20 Euros).

Note: they need to be replaced if they are cracked or show white icing, then they most likely will not work at all, and if, it 's very dangerous to use them. If they glow red when being used they will work, but should be replaced nevertheless.
They should not glow at all when new, and are still ok when they glow in blue color.



4) replace the selenium rectifier (optional)

Selenium rectifiers are to my knowledge archaic, and high risk components, and besides can emit highly toxic gases when they break.
Replacement silicon rectifier should be cheap anyways.

Question: has anyone found a replacement silicon rectifier readily available in Europe?



5) build a control knob (if missing)

according to what I have read the Spaceexpander will not work at all if this thing is missing. It is cheap and easy to build.
You just need a 250k pot (I'm guessing linear), a stereo 6,3mm jack and 3 wires. In the schematic it's also shown, but features an additional on/off switch, which you do not really need I guess.



6) find a reverb tank (if missing)

Luckily accustronics make a direct replacement, which should cost between 20 and 35 Euros, probably depending on the dealer.
The right model should be 4fb2b2c (medium delay) or 4fb3b2c (long delay).

Question: does it come with cinch connectors?



7) convert to European voltage (optional)

Question: has anyone ever done this, and does it make sense? (I would think yes)
according to the schematic the input transformer has an Input of 110V and an output of 290V and 6V.
Is there a direct replacement with an input of 230V?
Ones with 230V input and 230V+6,3V output are commonly available, would these do the job?
How do you run this thing in Europe?




I would be very happy if some more people could add some additional information on the Fisher Spaceexpander and if someone could help me to answer my questions.

greetings, and thanks for this amazing forum
Franz
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Neil C



Joined: 25 Feb 2004
Posts: 364
Location: Moonbase Alpha

PostPosted: Sat Mar 12, 2011 5:34 pm    Post subject: Re: Fisher Space Expander Restoration Checklist (please help Reply with quote

stranded horse wrote:


4) replace the selenium rectifier (optional)

Selenium rectifiers are to my knowledge archaic, and high risk components, and besides can emit highly toxic gases when they break.
Replacement silicon rectifier should be cheap anyways.


I asked about this issue on the Sound on Sound forum and Hugh Robjohns, who knows more about this sort of thing than we ever will, after looking at the schematic posted on this site, said there was nothing to be concerned about (and he's hardly the reckless type and he wouldn't give safety advice without being certain).
They were widely used in TV's up to 1975, and I don't remember the great selenium terror.
As I understand it you will really know about it if it fails (it smells), but it is not carcenogenic.
I guess if you are doing a full restoration then you might as well replace it, but it doesn't seem an imperative. I'd want it to stay for authenticity.

On the issue of power, you can just use a transformer, a lot easier than tinkering inside. Mine works fine in the UK.
eg (for the UK).
http://www.threedoubleyou.com/convertpower.htm

My new tank was the same in configuration as the original one ie. with chinch, or as I know them RCA, connectors.

The new medium tank I got seems to have a shorter reverb time than the original. I would be inclined to the long time version, but I can't guarantee that would be better.
As I noted in another thread, the new one sounds distinctly different to the original (I prefer the original).

I think most sold are working, it is a relatively simple device.
One of the most likely problems is dried caps, but try it and find out if there are problems, there may well not be. The only problem in mine was a slight hum and changing the valves sorted that out (although apparently the chances were higher that it was dry caps, it wasn't).
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interruptor



Joined: 04 Sep 2005
Posts: 1138
Location: Switzerland

PostPosted: Sat Mar 12, 2011 10:22 pm    Post subject: Reply with quote

Regarding power: I use an external step-down converter which plugs to the 230V net. It's a small device looking like a wall wart power adapter and costs about 20 Euro / 30 US$ . The 55W it can supply are enough for a Spacexpander.
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stranded horse



Joined: 07 Mar 2011
Posts: 65

PostPosted: Sun Mar 13, 2011 3:21 pm    Post subject: Reply with quote

interruptor wrote:
Regarding power: I use an external step-down converter which plugs to the 230V net. It's a small device looking like a wall wart power adapter and costs about 20 Euro / 30 US$ . The 55W it can supply are enough for a Spacexpander.


That seems like a waste of electricity to me though, transforming the 230V down to 120V and then up to 200V again, but it's probably the easiest way...
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stranded horse



Joined: 07 Mar 2011
Posts: 65

PostPosted: Thu Mar 17, 2011 1:51 pm    Post subject: Reply with quote

By the way, I've read that you need a preamp in order to avoid noise from the unit, and that you are using a vocal preamp. How much +db will it need? an expensive vocal preamp is no option for me, so I am thinking about building some kind of linear booster (I guess it makes around +16 to +20 db)
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Neil C



Joined: 25 Feb 2004
Posts: 364
Location: Moonbase Alpha

PostPosted: Thu Mar 17, 2011 9:08 pm    Post subject: Reply with quote

stranded horse wrote:
By the way, I've read that you need a preamp in order to avoid noise from the unit


You don't have to.
I just have line outs going into it (and the outputs going into line ins) and there is not a noise level I consider unacceptable.
Noise can be induced into the tank if it is near power or other electromagnetic sources, but moving it away will solve that.
You can hear my Spacexpander here (on the snare):
http://soundclick.com/share.cfm?id=1182041
Like some of your other queries, try your unit and then see if there are issues that need to be resolved.

I think Interruptor has rigged his with an input boost (not sure if you would put that before the control unit or the tank), and this may benefit the characteristic dub sound we want and may be something you do want to do, but it is not essential if your unit is working correctly.
As noted on this forum King Tubby modified his Spacexpander in some way and it has been guessed that a level boost into the unit may have been that modification.


Last edited by Neil C on Sat Mar 19, 2011 7:37 pm; edited 2 times in total
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interruptor



Joined: 04 Sep 2005
Posts: 1138
Location: Switzerland

PostPosted: Fri Mar 18, 2011 12:18 am    Post subject: Reply with quote

Hi

I am using an additional preamp between my "mixer aux send" (in fact it's the line output of my sound card) and the input of the spacexpander preamp. I do this because the lineout level of my sound card is rather weak. Of course you should try without a preamp first. As you are replacing critical parts on your unit chances are that you will have a low noise level compared to my unit anyway.
I don't know how much the gain is in db.

regards
Daniel / Interruptor
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stranded horse



Joined: 07 Mar 2011
Posts: 65

PostPosted: Fri Jun 10, 2011 1:31 pm    Post subject: Reply with quote

Ok, I didnt have time to finish the project until now.
I have replaced all the broken caps and all the electrolytics, no matter if they looked broken or not, because I assumed they were dried out. I replaced the 4 way cap with 4 single caps. I also had to replace a few resistors that were broken. I got the right tubes, the right spring can and everything, and made the pot, but it still doesnt work!
It turns on, but I get no reverb, only the original signal plus lots of noise. The noise goes almost away when I turn down the knob, but is still present.
I tried it with a guitar plugged into it, and the output of the unit into an amplifier. Two of the tubes have a tiny bit of red glow, but nothing what I would consider a brightly glowing tube.
What should I do now? Is there anyone here living in Germany or nearby who is experienced with this unit whom I could send it and who could take a look or something?
I put a lot of time and money into this project replacing all the broken parts and buying the missing ones and am kind of sad that it's not working now...

I hope someone here can give me some kind of advice.

regards, Franz
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