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Post by stringbean on Sept 27, 2008 10:25:28 GMT -5
When I recieved this back from Strouds Electronics,It was fine for 1 day and then this is what happened.It started popping through the speaker when I unkeyed.Then it started a pearcing screaching staticy noise very quickly when I ukeyed.Then the next time,it wouldnt stop.And I had to turn my radio off in order to stop it.Turned it back on,Same thing again.Put the radio up and planned on contacting strouds.Pulled it back out later,and its been fine for about a week or so.This morning,When I turned it on,the needle went over and came back as it usually does and started that loud staticy screach and woudnt stop until I shut it off again.Turned it on and of real fast,finally stopped and its been fine since other than the fact it seems to be popping a little louder than normal thruogh the speaker when I un-key.Thanx for any help and feel free to call me at 619-977-5672.Kevin
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Post by mrgumby OT21 on Sept 27, 2008 11:01:39 GMT -5
have you tried unplugging the microphone to see if it still happens
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Post by stringbean on Sept 27, 2008 11:42:02 GMT -5
No,I will try that next time it happens and see though.Thanx.
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Post by stringbean on Sept 27, 2008 12:53:33 GMT -5
It did it again and it didnt make any diference.
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Sandbagger
Administrator/The Boss 
Posts: 6,250 
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Post by Sandbagger on Sept 27, 2008 13:30:07 GMT -5
When I recieved this back from Strouds Electronics,It was fine for 1 day and then this is what happened.It started popping through the speaker when I unkeyed.Then it started a pearcing screaching staticy noise very quickly when I ukeyed.Then the next time,it wouldnt stop.And I had to turn my radio off in order to stop it.Turned it back on,Same thing again.Put the radio up and planned on contacting strouds.Pulled it back out later,and its been fine for about a week or so.This morning,When I turned it on,the needle went over and came back as it usually does and started that loud staticy screach and woudnt stop until I shut it off again.Turned it on and of real fast,finally stopped and its been fine since other than the fact it seems to be popping a little louder than normal thruogh the speaker when I un-key.Thanx for any help and feel free to call me at 619-977-5672.Kevin Almost sounds like a bad (sticking) relay. |
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Post by 2600 on Sept 27, 2008 14:07:33 GMT -5
There are two or more filter capacitors that will do this.
C449 is a 10uf 450 Volt axial cap on the "AA" pc board, also called the "auxiliary receiver" board, the one plastered to the right-hand side of the cabinet. Plugs into the main receiver board behind the VFO knob.
The other likely suspect is one section of C624, the short 4-section four-by-10 uf twist-lock can behind the speaker. Pretty sure it's the orange wire on that cap. You can follow the orange wire to the inboard edge of the main audio board to hole # B15. You can pull the orange wire from point B15 and put a 10 uf 450-Volt radial cap with the positive wire on B15 where the orange wire was removed, and the negative lead to ground near it. Odds are I have a pic of that "patch" somewhere, but my image archive is getting out of control. Would probably take an archeological expedition to track it down at the moment.
The section of C624 with the red wire on it can cause trouble, but if you have a way to check that all four sections have at least 5 or 6 uf of capacitance in each one, that's quicker. The red wire from C624 goes to point B26. Pretty sure B26 is on the edge of the audio board closest to the two multi-section 'can' filter caps.
Besides, if C624 is original, and one section is bad, the rest will follow soon.
We've been doing the 'scorched earth' on those for so long, that tracking down just one bad cap doesn't get done too often. Used to be that a horse trader who brought one in to 'patch cheap' so he could sell it would have this kind of patch job done. Just doesn't come up as often as it did 10, or 20 years ago.
Bit it's most likely one of these. The "works for a day or a week" symptom sure sounds like a 30 year-old electrolytic that took a day or three to wake up and 'remember' how old it is.
I'm used to just checking each of these to see if it's an open circuit before we apply power. Can't remember which ones will be affected by turning the volume control, and which ones will cause a noise that the volume control WON'T affect. Been too long.
73
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Post by stringbean on Sept 27, 2008 14:47:19 GMT -5
Thank you Nomad,you have a PM.
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Post by stringbean on Sept 29, 2008 6:04:05 GMT -5
Want to post that strouds did a great job and that in no way am I pointing a finger at them for this issue.
The problem has been solved and was a bad relay!!!!
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Post by mark4 on Sept 29, 2008 19:00:36 GMT -5
I have seen a similar problem with the relay.
After years of heat and contacts that may look like they are in excellent condition. I have come across a relay that the bottom board is warped. This may cause a problem with the alignment of contacts and the relay hanging up.
2600 has allot of great ideas here to keep note of. I would not even consider operating a Tram with all those old caps and resistors in it. I do hold off on changing the twist locks. Mainly because of frustration with the new ones not lasting a year before a section opens up. Contacted the manf. and they claim they have resolved the issue.
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Post by 2600 on Sept 29, 2008 22:43:38 GMT -5
Literally everything in that radio goes through the six circuits in that big relay.
Swapping in a good one will settle that question in a jiffy. If you have one on hand.
Glad to hear it was that simple.
No soldering iron required!
73
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Post by 2600 on Sept 29, 2008 22:57:50 GMT -5
Oh, and the failure problem with the tall 3-section filter can towards the rear has to do with the unloaded voltage from the power supply while the tubes warm up.
We had this problem with 450-Volt rated parts, so I looked at the voltage on them while the tubes are cold, for the first half-minute or so after the radio is powered on cold.
Jumps up to 475 or 480 Volts, before settling down to 400 or 410 once the tubes warm up and begin to draw normal operating current. Some of the 450-Volt cans we were buying would go bad in a year or two as a result of this brief exposure to voltage above the rating, every time you turned on the radio.
Solved this by using a two-section filter rated at 500 Volts. Best source is suppliers of parts for guitar amplifiers. This is the reason some older tube-type guitar amps would have a "standby" switch. You were supposed to set it to standby before turning on the power. After a minute to warm up, you would flip it to "operate". This created a demand for 500-Volt filters to serve that market. Since two of the three sections are tied together, the 2-section part is a 'drop-in" substitute. Only drawback is the need to drill out the rivets holding the original metal saddle that accepts the twist-tabs on the original-type can. Fortunately, the clamp that holds the new part has two feet that line up with the holes left when the rivets are drilled out. Two #6 screws hold the new part right where the old one went. A ground lug with lockwasher-style teeth in the screw hole provides a chassis ground for the black wire.
Not the only solution, but the one I prefer.
73
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Post by mark4 on Sept 30, 2008 20:19:30 GMT -5
I should clarify on the twist lock caps.
These were all replacements in brownings.
Keeping my fingers crossed for the Tram.
When this occurs in the Tram I will most likely stick with the original style. Just to keep it looking original. But if the same problem returns that may change my mind on this. I could never bring myself to alter the chassis yet. These a very rare truly mint radios. If it were a beater it would not be a issue.
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