Freeze Spray?
Is that like canned florida sunshine?
I tryd cooling it, It had no effect.
I do have all of the tube voltages now as listed below.
These measurements were made with tubes installed, Power on free standing on bench. Not attached to any source or output.
V1
pin1 - 130
pin2 - 0
pin3 - 1.35
pin6 - 131
pin7 - .19
pin8 - 1.37
V2
pin1 - 136
pin2 - 0
pin3 - 1.29
pin6 - 125
pin7 - .1
pin8 - 1.45
V3
pin1 - 278
pin2 - 2.8
pin3 - 52
pin6 - 278
pin7 - 2.9
pin8 - 53
V4
pin1 - 142
pin2 - 0
pin3 - 1.4
pin6 - 107
pin7 - .63
pin8 - 1.4
V5
pin1 - 143.5
pin2 - 0
pin3 - 1.4
pin6 - 112
pin7 - 0
pin8 - 0
V6
pin1 - 278
pin2 - 2.71
pin3 - 50
pin6 - 278
pin7 - 2.4
pin8 - 45.6
Channel B is not functioning and consists of V1, 1/2 of V3, V4, And 1/2 of V6
Based on schematic
Trout
Is that like canned florida sunshine?
I tryd cooling it, It had no effect.
I do have all of the tube voltages now as listed below.
These measurements were made with tubes installed, Power on free standing on bench. Not attached to any source or output.
V1
pin1 - 130
pin2 - 0
pin3 - 1.35
pin6 - 131
pin7 - .19
pin8 - 1.37
V2
pin1 - 136
pin2 - 0
pin3 - 1.29
pin6 - 125
pin7 - .1
pin8 - 1.45
V3
pin1 - 278
pin2 - 2.8
pin3 - 52
pin6 - 278
pin7 - 2.9
pin8 - 53
V4
pin1 - 142
pin2 - 0
pin3 - 1.4
pin6 - 107
pin7 - .63
pin8 - 1.4
V5
pin1 - 143.5
pin2 - 0
pin3 - 1.4
pin6 - 112
pin7 - 0
pin8 - 0
V6
pin1 - 278
pin2 - 2.71
pin3 - 50
pin6 - 278
pin7 - 2.4
pin8 - 45.6
Channel B is not functioning and consists of V1, 1/2 of V3, V4, And 1/2 of V6
Based on schematic
Trout
Are those numbers with respect to ground? If so, you've got some leaky caps and possibly faulty grid leak resistors. I'd go with the former. The voltages on the output cathode follower seem pathological- you'd want the grid to be showing a volt or two negative wrt the cathode, but your meter's impedance could be throwing that off. Check cathode to grid voltages of V6 directly.
Yep, all voltages are chassis/ground - persepective tube pins.
Q: should I be measuring all these voltages with the input open or shorted.
I took them all with nothing pugged into the unit other than the ac cord and tubes.
I know on my guitar amps, all the inputs short with no instrument, Thats why I ask
Trout
Edit, Since V6 is a shared valve, I should get very close to the same readings between the 2 halfs right?
The 1/2 controling Channel A is functioning great.
Im Soo confused LOLI do fine just building stuff, You would think a pre-amp would be a fairly easy thing to fix, well, maybe not haha
The schematic that came with the unit is dated 1959. The tubes that were in it are 1961, So its possible the schematic is upside down.
so v5 might actually be v4 and and so on.
For sure rule out the tubes unless its blowing them as fast as I change them.
I'll dig around a bit more.
Hmm leaky caps might be fun, Those are all bumble bee caps and very hard to get.
How leaky can they be before it stops working? C63A is on 1 channel, And C63B on the other.
I just looked at the unit again, Replaced V4 & V5 again, Still nutting, Perhaps Its a cold joint that has finally givin up. I'll try hitting them with an iron, Flow it a little, and report back later.
The channel as I mentioned before did come back briefly after a tube swap, but only for a minute or so. Additional tube swaps have yeilded nothing.
BBL
Gene
Hi Gene,
Take a small solder pick (thin metal rod, almost a needle point) and tighten up the contacts in the tube socket.
If you are going to sell it, then just fix the problem and down the road it goes (I hate suggesting that, but value and all). If you are going to keep it, replace those caps now.
-Chris
Take a small solder pick (thin metal rod, almost a needle point) and tighten up the contacts in the tube socket.
If you are going to sell it, then just fix the problem and down the road it goes (I hate suggesting that, but value and all). If you are going to keep it, replace those caps now.
-Chris
OK more info,
I removed the tubes 1 at a time to determine exactly which tube is on what channel.
I proceeded to take a bunch of old RCA tubes I saved up from old console pulls, Purposely bent the pins enough to make insertion into the socket snug.
Then, as I systematically removed and inserted each tube 1 at a time, I got to 1 valve and the unit suddenly put out a moment of full signal.
However, I was once again unable to duplicate this. I poked around with a chop stick a bit and yielded no change.
But, this very possibly may be a clue that I am near the source of the problem.
I can confirm at this point the tone( Stepped bass & Treble) controls are functioning. Each step yeilds a change. Balance, Volume and level pots seem to be functioning fine.
This entire tube section in this preamp is on a floating board suspended by rubber dampeners.
Most of the related resistors and bypass & signal caps are located on this turret board as well as the sockets. To me it is starting to look more & more like a bad connection someplace and not entirely related to the single valve I just happened to be pushing on when it came back momentarily.
Possibly an internally broken component?
I am a man on a mission now!! I could If needed replace every carbon comp resistor in this thing, I have them all! LOL
I may try installing temporary caps if I end up going that deep.
The sudden blast of operation has inspired me to beat this thing. When its on, It sure sounds sweet.
Trout
I removed the tubes 1 at a time to determine exactly which tube is on what channel.
I proceeded to take a bunch of old RCA tubes I saved up from old console pulls, Purposely bent the pins enough to make insertion into the socket snug.
Then, as I systematically removed and inserted each tube 1 at a time, I got to 1 valve and the unit suddenly put out a moment of full signal.
However, I was once again unable to duplicate this. I poked around with a chop stick a bit and yielded no change.
But, this very possibly may be a clue that I am near the source of the problem.
I can confirm at this point the tone( Stepped bass & Treble) controls are functioning. Each step yeilds a change. Balance, Volume and level pots seem to be functioning fine.
This entire tube section in this preamp is on a floating board suspended by rubber dampeners.
Most of the related resistors and bypass & signal caps are located on this turret board as well as the sockets. To me it is starting to look more & more like a bad connection someplace and not entirely related to the single valve I just happened to be pushing on when it came back momentarily.
Possibly an internally broken component?
I am a man on a mission now!! I could If needed replace every carbon comp resistor in this thing, I have them all! LOL
I may try installing temporary caps if I end up going that deep.
The sudden blast of operation has inspired me to beat this thing. When its on, It sure sounds sweet.
Trout
OK
I conceed victory to the marantz. It has beat me. I think at this point trying to go further without a signal gen & scope is basically beating myself over the head
So,
I guess for the time being, It will get wrapped in plastic,boxed up and put in a safe place until I either get the proper equipment to diagnois this unit, Or locate a tech that is both trustworthy and has era correct parts. Primarily good Bumble Bee Caps that may possibly need changed. I have all the carbon comp resistors but after hours of measuring the ones in the unit, They appear within spec.
After a week of tinkering its gotten where I think its a needle in the ole hay stack.
Thanks for all that helped!!
Gene
I conceed victory to the marantz. It has beat me. I think at this point trying to go further without a signal gen & scope is basically beating myself over the head
So,
I guess for the time being, It will get wrapped in plastic,boxed up and put in a safe place until I either get the proper equipment to diagnois this unit, Or locate a tech that is both trustworthy and has era correct parts. Primarily good Bumble Bee Caps that may possibly need changed. I have all the carbon comp resistors but after hours of measuring the ones in the unit, They appear within spec.
After a week of tinkering its gotten where I think its a needle in the ole hay stack.
Thanks for all that helped!!
Gene
Gene,
The scope and the signal generator are a great ideas!
You know... at its best, electronics is like flying at night with instruments... at its worst, like flying without instruments. The only time you can see, hear, feel, smell, taste anything, is when something has gone wrong.
Get a scope, and we'll learn ya on how to "see" with it.
Meanwhile you got $5K in the closet -
The scope and the signal generator are a great ideas!
You know... at its best, electronics is like flying at night with instruments... at its worst, like flying without instruments. The only time you can see, hear, feel, smell, taste anything, is when something has gone wrong.
Get a scope, and we'll learn ya on how to "see" with it.
Meanwhile you got $5K in the closet -
Hi Gene,
I have to agree with poobah. As a young fella I picked up a war surplus scope. I was very young then and simply can not imagine doing anything without at least a scope and meter.
They are not expensive and you should be able to pick something up inexpensively. Hamfest would be one place..
-Chris
I have to agree with poobah. As a young fella I picked up a war surplus scope. I was very young then and simply can not imagine doing anything without at least a scope and meter.
They are not expensive and you should be able to pick something up inexpensively. Hamfest would be one place..
-Chris
I have an old old scope, Its a monster from yesteryear for sure, most likely a lower end unit and even more likely not working correctly, I plugged it in once months back, The Tube does display some frankenstein lines but for sure the switches, and who knows what else are bad.
I did some searching locally for a shop but Finding referances is another thing entirely.
I found this place Deltronics and chatted with him briefly on the phone. He does have bumble bee caps in stock for service jobs like this. $20 bucks to check it out, Plus estimate ect.
Its easily worth throwing a few hundred at it concidering the possible return.
I dunno, Im scratchin my head and thinking about it.
I know I could mess it up as well as the next guy, But if its messed up and costs alot to mess it up, I would be a bit (insert profanity here) over it.
Gene
I did some searching locally for a shop but Finding referances is another thing entirely.
I found this place Deltronics and chatted with him briefly on the phone. He does have bumble bee caps in stock for service jobs like this. $20 bucks to check it out, Plus estimate ect.
Its easily worth throwing a few hundred at it concidering the possible return.
I dunno, Im scratchin my head and thinking about it.
I know I could mess it up as well as the next guy, But if its messed up and costs alot to mess it up, I would be a bit (insert profanity here) over it.
Gene
Hi Gene,
Most service guys are thinking of $$$ and how quickly they can get in and out. That's why you should do this yourself. Considering the possible return on investment, pick up a decent scope on Ebay, or a new low end model.
The last thing you need is a hack job. Remember, you may be able to split an old defective cap, gut it and put a new one inside, gluing it together. Nothing wrong with doing that.
-Chris
Most service guys are thinking of $$$ and how quickly they can get in and out. That's why you should do this yourself. Considering the possible return on investment, pick up a decent scope on Ebay, or a new low end model.
The last thing you need is a hack job. Remember, you may be able to split an old defective cap, gut it and put a new one inside, gluing it together. Nothing wrong with doing that.
-Chris
The Thing is,
I am not finding the culprit that is preventing the unit from running.
I sat around 4 hours again this morning taking additional voltage measurements and have no iron clad reason for channel B to be dead.
I tested as many of the resistors as possibly, Tinkered around and confirmed all the sockets are making contact from the tube pins to the internal connections.
V5
pin1 - 143.5
pin2 - 0
pin3 - 1.4
pin6 - 112
pin7 - 0
pin8 - 0 actually reads 1.4 ( I must have been on wrong scale)
Other than a couple of random moments of full function, The point of interruption is eluding me.
Channel B consistently produces a very very low somewhat distorted signal to the amp, But only if I raise the volume to nearly 100% . I confirmed it is actually B producing this sound by disconnecting both in & out of channel B from the amp and source.
I do have an EICO 324 signal generator I had planned on rebuilding knowing someday it might be needed. I guess now would be one of those times. It was built in 1950, I figure to replace all 19 parts shouldn't take long and I have them all.
When I got these audio units I was in the middle of testing my latest guitar amp build,
Chassis for 2X12 50W Combo
You would think if I could put this darn thing together from scratch, I should be able to fix a freaking pre-amp.
I always said, I could build darn near anything, But I cant fix nuttin lol
Gene
I am not finding the culprit that is preventing the unit from running.
I sat around 4 hours again this morning taking additional voltage measurements and have no iron clad reason for channel B to be dead.
I tested as many of the resistors as possibly, Tinkered around and confirmed all the sockets are making contact from the tube pins to the internal connections.
V5
pin1 - 143.5
pin2 - 0
pin3 - 1.4
pin6 - 112
pin7 - 0
pin8 - 0 actually reads 1.4 ( I must have been on wrong scale)
Other than a couple of random moments of full function, The point of interruption is eluding me.
Channel B consistently produces a very very low somewhat distorted signal to the amp, But only if I raise the volume to nearly 100% . I confirmed it is actually B producing this sound by disconnecting both in & out of channel B from the amp and source.
I do have an EICO 324 signal generator I had planned on rebuilding knowing someday it might be needed. I guess now would be one of those times. It was built in 1950, I figure to replace all 19 parts shouldn't take long and I have them all.
When I got these audio units I was in the middle of testing my latest guitar amp build,
Chassis for 2X12 50W Combo
You would think if I could put this darn thing together from scratch, I should be able to fix a freaking pre-amp.
I always said, I could build darn near anything, But I cant fix nuttin lol
Gene
Hi Trout. Do you have an FM tuner or portable radio? Maybe your TV is close by? Tune for interstation noise, use it as a source to the pre, wick up the volume and start comparing readings left and right with your DVM set to VAC. It won't tell you anything absolute or accurate but you will quickly find where the signal stops, which is really all you need to know.
Yep. Sometimes we psych ourselves in the face of complex problems and seek complicated solutions. Two weeks ago a put a radio station back on air with a pair of headphones and two pieces of cross-punch wire. Burn a sine wave to CD, hook the pre up to a CD player, hit repeat and go DVM hunting. It will almost certainly be obvious where the signal stops without need of a proper scope or gen. From the description I'm betting on something mechanical - short, broken wire or trace, open contact, etc..
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