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Hot enough to burn the paint off
- Thread starter 357
- Start date
Good lord. We used to run a 3CX3000A7 in FM broadcast service and the stack temperature never exceeded 42 C which is about 108 F. Even the 4CX5000A at 5000 watts continuous output never ran hot enough to blister paint. But then again I suppose we had MORE than adequate cooling whereas that amp may be on the edge and if run hard could run very hot.
Hello All: Yeah this ain't right. Got a neighbor a few miles down the road with a pair of 3CX1500A7's and when first fired it, it heated up the room NOT RIGHT!
After costly repairs and proper impedance matching and the proper bias circuit and tuning the amp settled down and did the usual output and with a Temp-O-Matic indicator on top the amp above the tubes it was around 95 to 105 F. Also installed meters to keep an eye on the grid current and other voltages and currents.
Hope your not over driving the amp. The thing to know is that a few more watts doesn't mean anything as it takes at least 6 dB or 4 times the power to show a real increase. So many operators have squeezed too many watts out trying to max it all out at the cost of expen$ive Tubes and transistors. Not worth it, unless you just have to see the watt meter go over farther.
Jay in the Great Mojave Desert
After costly repairs and proper impedance matching and the proper bias circuit and tuning the amp settled down and did the usual output and with a Temp-O-Matic indicator on top the amp above the tubes it was around 95 to 105 F. Also installed meters to keep an eye on the grid current and other voltages and currents.
Hope your not over driving the amp. The thing to know is that a few more watts doesn't mean anything as it takes at least 6 dB or 4 times the power to show a real increase. So many operators have squeezed too many watts out trying to max it all out at the cost of expen$ive Tubes and transistors. Not worth it, unless you just have to see the watt meter go over farther.
Jay in the Great Mojave Desert
Looks like the tank coil (turns 4 thru 7) closest to the Plate tune capacitor has been rather toasty as well as the plate tune capacitor.
I'd offer about $900.00 but I'm too lazy to drive to Ohio to pick it up.
And it could get hi-jacked on the drive home because it has "Mercury Reflectors" in it.
73's
David
I'd offer about $900.00 but I'm too lazy to drive to Ohio to pick it up.
And it could get hi-jacked on the drive home because it has "Mercury Reflectors" in it.
73's
David
Looks like the tank coil (turns 4 thru 7) closest to the Plate tune capacitor has been rather toasty as well as the plate tune capacitor.
I'd offer about $900.00 but I'm too lazy to drive to Ohio to pick it up.
And it could get hi-jacked on the drive home because it has "Mercury Reflectors" in it.
73's
David
That discoloration on the tune capacitor just looks like silver oxide to me. The capacitor plates look fine. That bar is silver plated and typically turn black over time. Not 100% sure about that tank coil however.
BJ radionut
Supporting Member and 6m addict
Several More on QTH 4 sale...I would buy there before I would ever buy an amp from Ebay...Unless I was buying for a very reasonable price and just consider it a "PARTS AMP" before it arrived.
MHO
All the Best
Gary
MHO
All the Best
Gary
Seems like a hint that it was used on AM using the "High" side, rather than the "CW" setting as recommended by Ameritron.
The odometer on a car won't tell you the difference between easy and hard miles, just the total.
But this paint job says "hard miles" to me. I wouldn't be surprised to find the grid-current safety-cutout circuit has been bypassed. That's the only way you can effectively overdrive this amplifier for very long. A popular mod for wattmeter worshippers running AM.
73
The odometer on a car won't tell you the difference between easy and hard miles, just the total.
But this paint job says "hard miles" to me. I wouldn't be surprised to find the grid-current safety-cutout circuit has been bypassed. That's the only way you can effectively overdrive this amplifier for very long. A popular mod for wattmeter worshippers running AM.
73
Looks like I guessed wrong on that one. More like the 15-meter ham band. Notice the four turns at the right half of the upper output coil. A bit darker than the rest?
Makes it sound more like he was a serious 15-meter DXer busting pileups.
So maybe the grid-current cutout is still connected.
Maybe.
The spring clamp on the plate cap sure is dark. From heat, maybe?
73
Makes it sound more like he was a serious 15-meter DXer busting pileups.
So maybe the grid-current cutout is still connected.
Maybe.
The spring clamp on the plate cap sure is dark. From heat, maybe?
73
The two silver plated ribbons going to the load cap and the tank coil are dark in places as well. that is because of the silver tarnish not overheating. IMHO the ONLY suspicious looking parts that look overheated are the top of the cabinet and possibly that anode connector but the anode connector looks evenly colored so I am not sure about that. I still think the black coloration of the silver plated parts is simply due to tarnish. I have seen MANY tank components look like that and they were never run hot. I still would be suspicious of this amp however for the top cover alone.
It looks like a partial rebuild.
The tarnished spot on the coil looks like a thumbprint - feedthrus are also looking too new for the "age"
Orange sticker shows something like 4-15-97 ... last service date? Or considering the "Newer" look to that orange sticker versus the black paper shredded sticker behind the coil - something isn't "Fading" right for temp and parasitic issues...
Perhaps the pass was a better option. You just don't know...
:+> Andy <+:
The tarnished spot on the coil looks like a thumbprint - feedthrus are also looking too new for the "age"
Orange sticker shows something like 4-15-97 ... last service date? Or considering the "Newer" look to that orange sticker versus the black paper shredded sticker behind the coil - something isn't "Fading" right for temp and parasitic issues...
Perhaps the pass was a better option. You just don't know...
:+> Andy <+: