Dis I get in over my head too soon?!?
I know enough about stereos (ohms, wattage, etc) to do high-end auto installs, but I don't think I've got a clue about my new venture. I wanted to take some some old parts and put them together to make a nice little tube guitar amp for the house. This is what I got:
http://cgi.ebay.com/ws/eBayISAPI.dl...MEWN:IT&viewitem=&item=200031653122&rd=1&rd=1
Along with a nice old 10" speaker from a console system built in 1953, I plan to build a custom cabinet and start playing. However, it looks like a tube is missing and I have no clue on how to find one to replace it on my own, and forget about me repairing it. I can solder just fine, but I wouldn't know what was broken...
Should I take this to a local shop to have it looked over, or should I just track down the missing tube and cross my fingers?!? I can track down a new power cord easily (I assume) and hard-wire the speaker in (it has an odd looking plug right now), but I'm not ready to learn all about tube repair yet...
I know enough about stereos (ohms, wattage, etc) to do high-end auto installs, but I don't think I've got a clue about my new venture. I wanted to take some some old parts and put them together to make a nice little tube guitar amp for the house. This is what I got:
http://cgi.ebay.com/ws/eBayISAPI.dl...MEWN:IT&viewitem=&item=200031653122&rd=1&rd=1
Along with a nice old 10" speaker from a console system built in 1953, I plan to build a custom cabinet and start playing. However, it looks like a tube is missing and I have no clue on how to find one to replace it on my own, and forget about me repairing it. I can solder just fine, but I wouldn't know what was broken...
Should I take this to a local shop to have it looked over, or should I just track down the missing tube and cross my fingers?!? I can track down a new power cord easily (I assume) and hard-wire the speaker in (it has an odd looking plug right now), but I'm not ready to learn all about tube repair yet...
Hi janikphoto,
Step one. Get a schematic and look it over. It's possible the socket is for a plug to another piece of equipment (like a projector). There would be a lamp supply and pickup cell connection. You may need to modify this for guitar use.
Don't wail on that poor speaker you have. It will come apart. An instrument speaker is another thing again.
Hey Joe! (burnedfingers), have you done this before? Tubelab would be another good member to look in here. Many others too many for me to think of right now!
-Chris
Step one. Get a schematic and look it over. It's possible the socket is for a plug to another piece of equipment (like a projector). There would be a lamp supply and pickup cell connection. You may need to modify this for guitar use.
Don't wail on that poor speaker you have. It will come apart. An instrument speaker is another thing again.
Hey Joe! (burnedfingers), have you done this before? Tubelab would be another good member to look in here. Many others too many for me to think of right now!
-Chris
Sy, your eyes and monitor are better than mine 'cause it just looks like a black round spot to me. The 5879 he lists is a 9-pin minature low noise pentode used as a microphone or other low level preamp tube. I don't see any minature tubes on the chassis but it might be inside the black housing which I'm guessing holds a photo-multiplier tube also. I can't for the life of me imagine what they would do with 3 25L6s. Two are probably in the output in push-pull but what are they doing with the third one?
If my memory serves me correctly (it rarely does anymore), Filmosound was a name Bell & Howell put on their early 16mm sound movie projectors. I think I remember seeing that in elementary school but that was a loooooooooooooooong time ago!
Also, and this is the most important part, with 3 25-volt and 2 6-volt heater tubes, this probably does not have a power transformer and therefore has one side of the AC line connected to the chassis. These are very dangerous in that if you plug it in the wrong way, you have the hot side of the AC line connected to the chassis. YOU CAN BE KILLED! If you figure out how to use this for guitar, you MUST get an isolation transformer to run it from.
Hope this helps.
Ken
If my memory serves me correctly (it rarely does anymore), Filmosound was a name Bell & Howell put on their early 16mm sound movie projectors. I think I remember seeing that in elementary school but that was a loooooooooooooooong time ago!
Also, and this is the most important part, with 3 25-volt and 2 6-volt heater tubes, this probably does not have a power transformer and therefore has one side of the AC line connected to the chassis. These are very dangerous in that if you plug it in the wrong way, you have the hot side of the AC line connected to the chassis. YOU CAN BE KILLED! If you figure out how to use this for guitar, you MUST get an isolation transformer to run it from.
Hope this helps.
Ken
thanks. three pins. And yeah, it must be the input for the projector. That was dumb of me not to think that... It has a mic input that the guitar will plug into, so I won't have to modify the input.
The old speaker won't be abused. It is a lot like other old speakers I've seen in old guitar amps, so I was hoping to give it a try and see how it does. If it doesn't perform well, I'll just get an eminence or other current speaker designed for guitar use.
I'm reading through everything on the noob stickie and hopefully I will be able to do more tube stuff as a hobby. Thanks for the help so far...
The old speaker won't be abused. It is a lot like other old speakers I've seen in old guitar amps, so I was hoping to give it a try and see how it does. If it doesn't perform well, I'll just get an eminence or other current speaker designed for guitar use.
I'm reading through everything on the noob stickie and hopefully I will be able to do more tube stuff as a hobby. Thanks for the help so far...
dnsey said:
hmmmm... interesting. I saw the transformer right next to a plug on the side and thought that was the only one for power. I figured this female plug right next to the transformer on the side of the amp had three prongs and was kind of oval shaped, like where a power cord would plug in, so the transformer must be for sonverting ac to dc. Since I don't understand tubes well enough yet, I suppose I could be confusing it with something else...
Now, this plug on the side may not lead directly to the wall outlet and I may have to get an outboard transformer as suggested aabove, but it is definitely where the power comes in. It is even marked 117 volts/50-60 cycles/0.9 amps next to this side plug. This round top plug must be for the audio input from the projector, since the only other input area is a mic plug on the side labelled 'mic'. I guess you could narrate during the movie?!?
Well, I was going to just find a plug and hook this thing up to the wall, but that sounds bad if this thing is sans ac/dc transformer. I'll shelve this project until I can find out a bit more. Anyone know what info I need to track down a schematic? The only things I know for sure is that it came from a supposedly working bell and howell filmsound projector. I found another (not exact same model, but same knobs, mic input, fuse location, and power plug on it. See the fuse and power plug area on this one:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=270046971712
Of course that one has the huge transformer like you say. Mine is labelled 10 watts on the bottom, and i assumed the small trans on mine was due to the low wattage.
I'm doing a good bit of guessing here, but I believe the small transformer behind what appear to be 2 of the 25L6-GTs is the output transformer. The 3 pin socket just behind the transformer is probably where the speaker plugged in. These types of connectors were pretty common on old radios and amplifiers intended to be used as a part of a piece of equipment and not as standalone.
Since there is a connector on the side labeled "117 VAC 50/60 CY.", I'd bet lots of money that is the power input and was probably connected to an umbilical from the projector. If the connector is oval like you say and has 3 pins with the center one offset from the outside two, this was a very common power connector (HP used them of almost all of their test equipment before the current IEC connector became popular) and the power cord to fit these is now very hard to find. I just looked at the power connector on the other amp on ebay and all 3 pins are in a row; I think a mate for this connector will be very hard to find.
It would have been quite unusual for them to use 25-volt heater tubes in an amp with a power transformer. If you look at the tube line-up listed for the other amp you showed on ebay, they are all 6-volt heater tubes except the 5Y3 rectifier. The perforated covers on the chassis also point to it needing lots of ventilation and could be over power resistors used for dropping heater voltage.
One other thing, the tube he lists as a "65L7-GT" is probably a 6SL7-GT. I think the best advice has already been said; try to find a schematic of the amp or, if possible, the whole projector. Good luck.
Ken
Since there is a connector on the side labeled "117 VAC 50/60 CY.", I'd bet lots of money that is the power input and was probably connected to an umbilical from the projector. If the connector is oval like you say and has 3 pins with the center one offset from the outside two, this was a very common power connector (HP used them of almost all of their test equipment before the current IEC connector became popular) and the power cord to fit these is now very hard to find. I just looked at the power connector on the other amp on ebay and all 3 pins are in a row; I think a mate for this connector will be very hard to find.
It would have been quite unusual for them to use 25-volt heater tubes in an amp with a power transformer. If you look at the tube line-up listed for the other amp you showed on ebay, they are all 6-volt heater tubes except the 5Y3 rectifier. The perforated covers on the chassis also point to it needing lots of ventilation and could be over power resistors used for dropping heater voltage.
One other thing, the tube he lists as a "65L7-GT" is probably a 6SL7-GT. I think the best advice has already been said; try to find a schematic of the amp or, if possible, the whole projector. Good luck.
Ken
Here you go - sure to be here somewhere (or something very similar)!
http://www.film-tech.com/warehouse/index.php?category=2;rt=1162474762770]http://www.film-tech.com/cgi-bin/externallink.cgi?http://www.film-tech.com/warehouse/index.php?category=2;rt=1162474762770[/URL] EDIT: It's an odd link, which doesn't seem to work eternally!
Go to the second uRL, and scroll to "16mm projectors" (near the end of the page. I should think yours would be in the "B&H amplifiers model 120..." manual.
http://www.film-tech.com/warehouse/index.php?category=2;rt=1162474762770]http://www.film-tech.com/cgi-bin/externallink.cgi?http://www.film-tech.com/warehouse/index.php?category=2;rt=1162474762770[/URL] EDIT: It's an odd link, which doesn't seem to work eternally!
Go to the second uRL, and scroll to "16mm projectors" (near the end of the page. I should think yours would be in the "B&H amplifiers model 120..." manual.
I see what you mean... That round three prong plug on top could be an output to a built-in speaker, or maybe it is a mono input/output with a shared negative wire?!? I still think it has at least SOMETHING to do with input, since the ONLY other places I see for input are the 1/4 mic plug (labeled mic input) and the three straight prongs plug on the side next to the power input info (which leads me to believe it is for power input).
On the front side, there are volume, tone control, on/off switch, and mic input. Those are very self-evident what they do.
There are two plugs on the other side with the power input and fuse that are labeled for external speakers. One says 8" & 12". The second says 6" & dual. My guess is that the two diff plugs are set up for two diff ohm speaker outputs?!? Each plug only has two prongs, so it is for choosing one mono speaker (an 8" or 12" as one plug as stated). On this same side, there are the 117 volt/0.9 amps markings, along with something labeled Part 05973. Maybe this part number will help me find the exact schematic?
I looked over the links posted above and they look helpful. Thanks... You all have already given me more info in a few posts than I could've found in a day of searching on my own...
On the front side, there are volume, tone control, on/off switch, and mic input. Those are very self-evident what they do.
There are two plugs on the other side with the power input and fuse that are labeled for external speakers. One says 8" & 12". The second says 6" & dual. My guess is that the two diff plugs are set up for two diff ohm speaker outputs?!? Each plug only has two prongs, so it is for choosing one mono speaker (an 8" or 12" as one plug as stated). On this same side, there are the 117 volt/0.9 amps markings, along with something labeled Part 05973. Maybe this part number will help me find the exact schematic?
I looked over the links posted above and they look helpful. Thanks... You all have already given me more info in a few posts than I could've found in a day of searching on my own...
So, once I get my cabinet built and my speaker mounted, is there someone here I can pay to get the power supply up and running? I am not sure that I am ready to tackle this yet, but I want to use it. In the meantime, I think I will continue reading those noob primers in the stickie above and then find a project I am ready to do... Am I just being too nervous about this, or am I being smart?
Don't sweat it at all....you already have the primary component (Amp), the power supply is really a no brainer...any of us can coach ya into making one....if you know which end of a soldering iron to use we can help.
The one thing we do need is an accurate, documented (Written) voltage value that we need, & where to hook it in.
Jump over to the tube section or the power supply section & do some reading...nothing too long winded just get a feel for it.
______________________________________Rick...........
The one thing we do need is an accurate, documented (Written) voltage value that we need, & where to hook it in.
Jump over to the tube section or the power supply section & do some reading...nothing too long winded just get a feel for it.
______________________________________Rick...........
Thanks. Yup, I can solder well enough. I successfully replaced some components/switches on my fender princeton chorus amp, and they had a ton of tiny pins to de-solder and re-solder. This piece should be a piece of cake compared to it. I've also changed out power supplies in a european stereo component (from a donor 110 volt cd changer to the same model line working 220 volt cd changer).
However, I don't know how to calculate which transformer to use or anything... I will continue in the reading, then take lots of photos of where i think things will solder up, and finally ask more questions... Thanks...
However, I don't know how to calculate which transformer to use or anything... I will continue in the reading, then take lots of photos of where i think things will solder up, and finally ask more questions... Thanks...
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