| "New" 300-5 PA head [message #21527] |
Fri, 26 September 2014 08:19  |
fieldflower
Messages: 71
Registered: July 2004
Location: Sweden
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Member |
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Hi,
Long time no see...
Still have and use my 250-4 and cab, but yesterday added a 300-5 PA head to the collection.
Haven't even fired it up yet, but looking for some info on the in's and out's of these things.
The outside is in fair condition - handles and knobs all intact, but missing one metal foot and some tears in the TnR. And no stand. It has been rebuilt to swedish 230 V at some point, and by the looks of the (3 prong) cord it may have been a direct import when it was new.
Dating. It has serial number 106126. Does anyone know when it was made?
How does the anti-feedback knobs work? Is it 1 preset frequency per knob, turning the knob cuts more and more, and pulling the knob is on/off per frequency? Or is it working in some other way?
I see a footswitch jack on the back - what was the function of the footswitch? Reverb on/off? Anti-feedback on/off? Something else?
Also the lights in the blue buttons don't work. I guess it's the same type as in my 250 amp?
Not sure if the reverb even works on this thing - the handle on the back is missing.
This leads me to my next question - how do You open this thing? I might just trial-and-error myself to wisdom on this one, but if You see the question within shortly..
/Peter
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| Re: "New" 300-5 PA head [message #21531 is a reply to message #21527] |
Fri, 26 September 2014 09:46  |
stevem
Messages: 4775
Registered: June 2004
Location: NY
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Senior Member |
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fieldflower wrote on Fri, 26 September 2014 08:19Hi,
Long time no see...
Still have and use my 250-4 and cab, but yesterday added a 300-5 PA head to the collection.
Haven't even fired it up yet, but looking for some info on the in's and out's of these things.
The outside is in fair condition - handles and knobs all intact, but missing one metal foot and some tears in the TnR. And no stand. It has been rebuilt to swedish 230 V at some point, and by the looks of the (3 prong) cord it may have been a direct import when it was new.
Dating. It has serial number 106126. Does anyone know when it was made
The amp is a late 1973 made right at the end of the tuck and roll stuff!
How does the anti-feedback knobs work? Is it 1 preset frequency per knob, turning the knob cuts more and more, and pulling the knob is on/off per frequency? Or is it working in some other way?
The good fellow Kustom nut pleat may have info from the amps instruction booklet he can pass on to you.
I see a footswitch jack on the back - what was the function of the footswitch? Reverb on/off? Anti-feedback on/off? Something else?
Yes it's for the reverb on and off.
Also the lights in the blue buttons don't work. I guess it's the same type as in my 250 amp?
Yes they take the same GE 335 lamp.
Not sure if the reverb even works on this thing - the handle on the back is missing.
This leads me to my next question - how do You open this thing? I might just trial-and-error myself to wisdom on this one, but if You see the question within shortly..
The handle you speak of is to lock the reverb for transport and if that is broken off than the reverb will not work right
/Peter
[Updated on: Fri, 26 September 2014 09:48] Report message to a moderator |
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| Re: "New" 300-5 PA head [message #21536 is a reply to message #21533] |
Fri, 26 September 2014 12:00 |
fieldflower
Messages: 71
Registered: July 2004
Location: Sweden
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Member |
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stevem wrote on Fri, 26 September 2014 17:19I posted the lamp spec, it is a GE 335.
The rattle you hear in the amp is like I posted, it's the muting cup that came off when the reverb lock handle broke off, and yes you will get some reverb with the broken parts in there but it will be limited.
If you want to date the amp to the tee than both the power transformer and the two big can type power supply filters will have a 6 number digit date code on them, the 4th digit is the year, and the next two are the week of production !
Hi,
Sorry, I must have been writing my follow-up post when You posted Your reply...
Great to hear the year and lamp specs.
The buttons were really hard to get to for changing the bulbs, so I doubt I'll be changing those.
Unfortunately - I really like to have the lights glowing.
(I can change one of them, but the power button is cramped between the faceplate and the riveted inner wall protecting the power stuff.)
A little surprised it was 1973 - I thought they used the last digit for year.
But I believe You - 1973 it is. I don't really need more exact than that - happy with the year. If I open it up again I'll check the power transformer and filters.
A little fun that it's the same age as my 250.
After figuring out it was the same way of opening as the 250 - screws from the bottom and slide out - I got more puzzled...
The rattling was one of the nuts for the reverb pan - good to get that one fastened.
But the reverb didn't have a transport pad (there are no holes at all on the backplate where a handle could go), and the outlet I thought to be the remains of the handle turned out to be an output or input jack.
The jack is plastic and looks new-ish, and the jack is not marked on the back, so I guess it's a mod of some sort. Now if I could only figure out what it's for...
Good news that the reverb is spick-and-span, but another mystery to solve...
There were 2 very thin leads coming from that jack, and they ended up somewhere in the middle of the board, right behind the reverb master knobs somewhere. Before entering the board they had some sort of 1/2 inch orange square plastic components.
I'm really not good at electronics, so I have no idea what those are, but suspect they are good clues to what the jack is likely to do.
I could trial-and-error the jack, but a little hesitant to try if it's a footswitch jack - not good shorting it if it's something that doesn't like being shorted...
Any guesses are most welcome!
There were some different types of hissing when I ran it - would be good to hear if it's normal or if I can improve in any way.
1. When cranking the master treble there was a high pitch hissing that was very noticeable. Not at all the same when raising the channel trebles, although both methods resulted in the same sound characteristics.
Overall a quite murky sound, so a cranked treble is required for the amp to sond "normal".
Something wrong overall making it sound murky? Or something with the master treble?
2. When cranking the reverb intensity above 9 o'clock there was a distinct hiss/hum.
It could be slightly changed by changing the reverb bass and treble, but the intensity knob made 95% of the difference.
At 12 o'clock it was annoying in volume.
The best reverb I get when going full on reverb bass and treble, keeping below 9 o'clock on intensity, and putting the channel reverb buttons at 12 o'clock or so.
Also I don't really understand what the master volume knob does...
It behaves more like a mid than a volume. When fully off it's still possible to play just fine, just with slightly less volume.
[Updated on: Fri, 26 September 2014 12:02] Report message to a moderator |
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| Re: "New" 300-5 PA head [message #21542 is a reply to message #21536] |
Fri, 26 September 2014 13:35 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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fieldflower wrote on Fri, 26 September 2014 11:00The buttons were really hard to get to for changing the bulbs, so I doubt I'll be changing those. If you are careful, you can pull off the blue lamp cover from the front of the amp to change the bulbs.
fieldflower wrote on Fri, 26 September 2014 11:00But the reverb didn't have a transport pad (there are no holes at all on the backplate where a handle could go), and the outlet I thought to be the remains of the handle turned out to be an output or input jack. It may be that the tank has been replaced and the transport parts have been removed. Does the open side of the tank face the back panel of the chassis?
fieldflower wrote on Fri, 26 September 2014 11:00There were 2 very thin leads coming from that jack, and they ended up somewhere in the middle of the board, right behind the reverb master knobs somewhere. Before entering the board they had some sort of 1/2 inch orange square plastic components. This may be an output or input jack to the reverb section. Like an FX loop, MAYBE. Any markings on the orange square components?
fieldflower wrote on Fri, 26 September 2014 11:00When cranking the reverb intensity above 9 o'clock there was a distinct hiss/hum.
It could be slightly changed by changing the reverb bass and treble, but the intensity knob made 95% of the difference. If the tank has been replaced it may be mounted in the wrong orientation. If this is so, there will be more hum than normal.
fieldflower wrote on Fri, 26 September 2014 11:00Also I don't really understand what the master volume knob does...
It behaves more like a mid than a volume. When fully off it's still possible to play just fine, just with slightly less volume. Try pulling out on the knob. There is a switch that should allow the volume to go to zero.
If you haven't done it yet, go to the literature section and under the Other tab you will find catalogs for your amp with some basic information.
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| Re: "New" 300-5 PA head [message #21544 is a reply to message #21527] |
Fri, 26 September 2014 14:22 |
stevem
Messages: 4775
Registered: June 2004
Location: NY
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Senior Member |
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To replace the bulb push the blue lamp cover off each switch from the inside of the amp.
To replace the bulb many times I slip on some automotive vacuum hose to both remove the old bulb and install the new one.
When you install the new bulb apply some grease to it so that it does not corrode to the socket .
The amp should have a blank reverb lock hole if the T shaped handle is missing!
All of the jacks on the amp sit 3/4 of a inch off of the bottom of the amp, left to right you have the reverb foot swt jack just to the right of the serial number plate, then the next two jacks right next to each other are the speaker jacks, the next jack two inches more to the right is the monitor output jack, a little more to the right of that and 4 inches above that should be the reverb lock handle hole.
I do not know what you mean by a plastic jack unless on of the original metal ones have busted and was replaced.
The brown wire off of the first jack on the left is the reverb foot swt and goes up to the center front main board.
The orange wire off of the last jack goes to the output driver board ,there are 3 male spade terminals on the front left side of that board and the orange wire goes to that first left terminal.
The master volume in the fronts center control section should be able to cut the overall volume of the heads output to zero while not effecting the tone, if this is not then that main board likely has a problem!
Your hum issue when your turned up could be due to two things,1) the wires are plugged into the wrong end of the pan, 2) and or the pan has been re installed the wrong way, the if the pan is still the original then the RCA jacks should face the bottom of the amp.
The way the pan should be mounted is to have its RCA jack marked as output be on the side of the Amp that is away from the power transformer and the choke that is right next to it .
[Updated on: Fri, 26 September 2014 14:27] Report message to a moderator |
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| Re: "New" 300-5 PA head [message #21546 is a reply to message #21544] |
Fri, 26 September 2014 15:36 |
fieldflower
Messages: 71
Registered: July 2004
Location: Sweden
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Member |
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Aha, being able to take the knobs off that way makes it more doable.
It may have been the way I did it on my 250, but that's some 7-8 years ago now...
(From reading my own posts from back then) it seems I used the electric shrink tube trick then.
OK, so bulb change is on again.. 
The back of the unit is not showing any holes that could have been for a reverb transport handle.
There are the holes at the bottom for output, tape, monitor, footswitch.
There are the fuses.
And there is this one-off hole that seems to be a mod of some sort.
I initially thought it was a remnant from a reverb transport handle, but the placement makes me think not.
When looking into the amp from the front:
1. the left part of the back wall holds the reverb tank on, what seems to be, an original mounting thingy with nuts.
2. The right part holds the high voltage stuff which is in its own metal room, which is riveted to the back plate.
3. Inbetween these there is a 1,5" gap, and this is where this mystery hole/jack is. The hole is about 2/3 up on the back plate.
The jack is metal on the outside, but on the inside it's a plastic molded unit (not the open contact surface jacks that are used everywhere else in the amp.)
Have closed the amp up again, but will check if there is any printing on the square orange thingys next time I open it.
The reverb pan has a full metal side facing into the amp - didn't check if it was open towards the back plate.
Next time I will definitely try to switch side on the reverb connectors and see if the hum changes.
The wires are coming out on the right side for reaching the connectors, so I doubt it's wrong side up. Will check next time I open it. Or did You perhaps mean change so the part facing into the amp should instead face the back plate? Didn't pay attention if it's doable to swing it around that way...
The master volume certainly doesn't cut down volume to zero - it behaves like a trim volume or something.
Tried pulling on it, but it's not a push/pull. Only the anti-feedback are.
I guess there could be a connection between the mystery jack and the odd behaviour master volume (and possibly hum)...
Edit: The inside of the amp is in very neat condition. The original schematics were still in there.
And the suspected mod parts were neatly soldered and the orange thingys glued to stay put.
It gives me a sense of some level of professionalism from the one who has altered it.
But it's hard to say what this person wanted to achieve, and what he was willing to sacrifice to get it...
[Updated on: Fri, 26 September 2014 15:56] Report message to a moderator |
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| Re: "New" 300-5 PA head [message #21547 is a reply to message #21546] |
Fri, 26 September 2014 20:50 |
pleat
Messages: 1454
Registered: June 2004
Location: Belding, Mi
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Senior Member |
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The master controls. Three anti-feedback pull on push off. The master section is Bass-Volume-Treble and the master reverb section Bass-Intensity-Treble.
The anti feed back is divided into three sections A-B-C or bass mid and treble. Depending on the feedback, if it a low rumble, then pull on the A feedback control and rotate it until the low rumble is eliminated. If the feedback is high pitched, the use C and sweep the control until the feedback is gone. It's basically a three band sweepable EQ.
I'd start with all feedback controls off, set all rest of the master controls to 12 o'clock. The master volume should bring the amp to dead quiet with the control off. Not sure what going on with your amp.
Once all the channels are set and you find the overall mix needs a little more bass, it's much easier to grab the master bass control to get the tone you want. Same with the master reverb controls, they provide a quick overall tonal change. The poor tone of the reverb tank and hum might be the tank is a replacement or was mounted backwards causing the hum.
Towards the end of the T&R kustom amps just before the hard tolex covered amps came out, Kustom was not using the reverb lock anymore. Too many reverb springs would get trapped behind the locking disc and when unlocked would break the spring clip at the transducers.
I use clear plastic tubing for an Aquarium setup. Just the right size for the bulb, and it also works great for guitar control pots that need to be removed from a F hole or thin hollow body guitar.
pleat
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| Re: "New" 300-5 PA head [message #21786 is a reply to message #21527] |
Thu, 30 October 2014 17:19 |
chicagobill
Messages: 2006
Registered: April 2003
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Senior Member |
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Looking at the photos, the blue wire is connected to C13 which is connected to output of the reverb drive circuit. The red wire connects to an unused input/mixer resistor R42.
So whichever contact of the jack is connected to the blue wire tip or ring, that is a signal send. The contact that is connected to the red wire is a signal return.
This is based on the photos and the board layout image. You should double check the connections, as the ends of the yellow cap wires are not clearly visible.
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| Re: "New" 300-5 PA head [message #21791 is a reply to message #21527] |
Sat, 01 November 2014 07:45 |
fieldflower
Messages: 71
Registered: July 2004
Location: Sweden
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Member |
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Cut off the extra leads close to the board.
All oddities still there though... 
- Still sort of murky sound.
If I go past 50% on master bass/treble I get a little hum/hiss. I think it's on pretty normal level for a -73 amp, but if cranking the treble to 100% it's a little annoying.
Channel bass/treble I can turn all the way up with no added hum/hiss.
With master bass/treble at 50% and channel bass/treble at 100% I get the normal open sound I would have expected around 50% on all tone knobs.
Is it just so that these amps are a little murky so they wouldn't hiss out of the big horn speakers? How does Yours sound?
Edit: Tested with microphone, bass and acoustic guitar, and perhaps it isn't so murky sounding. I have tested on electric guitar before now and may have had the "bright" sound in mind... With these other instruments 50% bass/treble was actually a good starting place.
- Master volume still doesn't make sound go down to zero.
In fact with channel volume on 50% or so the electric guitar get really loud with master on 0.
Of course if I put master volume on 50% as well it gets REALLY loud.
- Reverb is humming if I put master reverb intensity past 10 o'clock.
No change in hum tone/volume regardless of master reverb bass/treble.
No change in hum when putting channel reverb at 100%.
I tried changing the reverb connectors, but they were clearly the right way from the beginning.
With master intensity on 10 o'clock, bass and treble at 100%, and channel reverb at 100% I get a clear pretty saturated reverb (a little more than needed for most guitar/vocal/etc)
- When I power off the amp the crack out of the loudspeaker is LOUD.
I'm afraid to blow the speaker from this sound, so (apart from testing if it's still there) now I remove the speaker lead before switching off.
Is that the way these normally behave? My 250 makes a lot softer sound on power off.
I'm a little surprised the oddities didn't go away when removing the mystery jack.
I can't see any other signs of modifications in the amp (apart from the re-done main power change to european 240 Volt, but that looks to be done in exactly the same way as on my 250. On the back side I can even see remnants of the same sticker I have on my 250, indicating it was done professionally. I believe both were imported to Sweden brand new by the same music reseller back in the day.)
But at least now I have the blue lights functioning. 
[Updated on: Sat, 01 November 2014 09:04] Report message to a moderator |
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| Re: "New" 300-5 PA head [message #21793 is a reply to message #21527] |
Sun, 02 November 2014 07:23 |
stevem
Messages: 4775
Registered: June 2004
Location: NY
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Senior Member |
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Well the loud crack at power down would lead me to take a educated guess that you have a leaky bypass or coupling cap.
If you can read a schematic which we have for the amp on this site and you have a voltmeter you can check out voltages around the 40 volt and 12 volt power supply rails and the same at the same time check the voltages around all the caps i posted about.
Also if you do have a voltmeter set it for dc volts and hook it across the speaker and if at turn off that voltage crack is over 25 volts than I would unhook the speaker when shut the thing off!
[Updated on: Sun, 02 November 2014 07:27] Report message to a moderator |
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| Re: "New" 300-5 PA head [message #22968 is a reply to message #21527] |
Sun, 24 May 2015 15:50 |
fieldflower
Messages: 71
Registered: July 2004
Location: Sweden
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Member |
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A little update, and some more stuff to dig into...
I haven't managed to take the PA to my dads for a checkup yet...
But I by coincidence happened to buy another one today, but one that's missing the whole wooden box with the TnR, and in a little worse shape at that.
Only one of the fuse holders had a fuse, but it was a 2A instead of a 3,15A.
But when scavanging the other PA for fuses to try it out I saw that one of those were actually shot. (When putting them back afterwards I put in the 2A fuse instead of the broken one and then power-up pop was milder than the pistol shot bang from before.)
The new one then fired up.
Of course the blue lights didn't work, but I have bulbs left from before so that's fine. The buttons were in fine condition, so those should work once replaced.
But it had a thunderous humming I didn't like a lot. Seems to be a bunch of pots with corrosion, with the master bass pot the king of them all. After massaging that one for a while and avoiding the worst areas it calmed down a little.
The reverb doesn't seem to work. Full on reverb on both master and channel didn't produce any reverb at all. It looked ok on the inside, the little that can be seen.
Is it normal for a non-functioning reverb to simply not change the sound at all, or should it be expected to produce hum/weaker signal/etc?
What could be wrong with it?
This PA is also one of the later models that doesn't have the transport pad thingy.
I guess the first I should check is the foot switch jack so it's not shorted in some way so it doesn't turn on...
Missing a couple of knobs, and some of them are much too easy to pull off.
This one also had the problem of not cutting the volume down to zero when putting the knob at zero.
But then when fiddling with that the master volume made a "click" and then it was really silent...
Trying the same on my first PA - of course it clicked down to zero too...
So the mystery of the no-real-zero-volume is resolved...
Feels a little bit stupid, but it's the first click-to-zero pot I've seen on these.
Both PA's produce a rather loud cracking sound from the speaker on power-off, but I'm pretty sure it's mellowed somewhat in the first one - perhaps due to replacing the shot fuse..?
But the first PA now is a lot nicer on power-on. It's much more of the soft thump+reverb sound that I get from my K250.
The plan for the first one is still to take it do my dads and check it up.
The TnR on the bottom is badly torn, so I'll fix that up.
And then it's pretty much done.
The plan for this second one is to
1. Clean/affix all jacks, try to smoothen up the pots with massage and cleaning alcohol, replace the bulbs and the fuses. = Get it working. Perhaps with some of dad's TLC.
2. See if I can find the reason for the reverb not working (and fastening it - it's hanging on 2 bolts now). = All functions working.
3. Cleaning it up real good on the front and back plate, replacing the knobs (probably all of them with brand new).
4. Build a new wooden box and make my own TnR, most likely with zodiac naugahyde (having a really hard time choosing colour).
5. Build a couple of 4x12 speaker columns (I will bug You for measurements later  ) and make them matching TnR.
(The TnR making is very much depending on if the wife's sewing machine can stand sewing in naugahyde...)
It would be such amazing fun to not only resurrect the new PA but make it complete and shiny.
We'll see how far I get...
Long post, but I had to let out some excitement...
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