This ones gonna be a little winded so bear with me. EPT690010C Picked this up for next to nothing previous owner said he was running a palomar 300 amp, amp went kaboom his words next day got the amp out of line fired up the radio no tx had a bad storm that night doesn't know if the amp killed it or lighting so I rolled the dice and brought it home. Hooked it up for a check up It's got excellent receive on freq, pa has strong audio, zero tx on the meter so I hooked up the monitor radio and sniffer got nothing. Started inspection and found that the PO must have tried to repair it, really ugly, parts missing traces gone and blow torch soldering. OK got to work repaired the ugly, it was missing a few ceramic caps and the pre driver I didn't have a 2538 that it calls for but I had a good 1973, (I figured close enough for testing) 2166 good 1 2312 was bad replaced it, checked all the voltages in the pa section and the sb754 everything responded correctly, so fired it back up no tx on meter but now have a signal on the monitor radio with good modulation on am and ssb. I set the rf gain on the monitor to zero with sniffer at the pre driver i get 20db signal, checked the so239 with the sniffer same 20db signal. I think the pa section is good but being a little anal retentive I've started checking the individual components in it anyway, I'm about 3/4 of the way through it no faults yet. The last one of these I did had the same symptoms turned out to be missing freqs so I did a mini alignment just to see. pll section checked good everything responded freqs are off only a .01 to .04 good enough for now. Moved on to the tx section sniffer by the pre driver L44 to L40 all had good peaks except L43 (I have a replacement). driver bias will come up to 25ma at max, finals will come up to 75ma at max, tx freqs are close enough for now 27.205.04 tx. It acts like there is no drive getting to the finals, with the rx and tx being on freq and responding to adjustment I,m assuming ft1,2 and 3 filters are ok and ic 1 should be ok correct me if I,m wrong on that. So I'm leaning to ic9 mixer smd tda6130 5x4 on solder side of the board. I looked at the dx99v with the 3600 board it uses the 6130 dip chip on the 14c board and has voltages listed do anyone think the voltages would be the same between the dip chip and the smd chip and the 2 different boards, just trying to find the correct voltages to check ic9 mixer, not 100% sure it's the problem but would like to eliminate it. This is just my preliminary testing, I'll go ahead and replace L43 and continue with the pa section r&r. If I've missed something kick me in the arse and say hey dummy check this first brain is mush taking a break for now. Greatly appreciate any and all help. Thanks Ira
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Galaxy DX2517 basket case (almost)
- Thread starter ira parker
- Start date
This is where a 'scope pays for itself
Having a way to "follow" the signal downstream stage by stage would be an enormous asset in pinning down this fault.
73
If you can hear your signal on a monitor radio, this chip is almost certainly okay. It fails VERY rarely, and you transmit signal is most likely being lost downstream from that chip.
Having a way to "follow" the signal downstream stage by stage would be an enormous asset in pinning down this fault.
73
Well that is music to my ears as there is no information on trouble shooting it at all. the voltage charts that are available are not specific to this chip and have contradicting pin outs and voltages between schematics! Also this chip seems to be at an end of life status and only available from across the pond. Thanks Nomad I just wanted to eliminate it as a possibility, which I had eliminated it in my head but when L43 wouldn't show a peak I went back and checked voltages on it, the voltages are there but not in the same pin configuration as the schematic and voltage charts I was using so I started to second guess myself so here I am looking for some confirmation. As noted this is just my preliminary investigation since the PO said it was hooked to a palomar 300a that went kaboom, those 300a's had back splash issues from the relay much less what could have surged through the radio upon a major failure so I wanted to check all the ic's and #9 was the last one in line. So next step will be injecting a signal from the oscillator and running through the PA stages with the scope don't know if I'll get to it today gotta do a little hurricane prep today around the house. What is your opinion on the 1973 predriver replacement vs the 2538 that was in it (that 2538 is at end of life also) I've seen this configuration used in many radios (1973,2166,2312,2312) once again thanks for the input puts my mind at ease. Ira
OK had a few minutes to hook up the old heath kit oscillator 10-32mhz added some modulation to produce a nice wave form injected it into the so239 started from there and moved thru the coils L28 to 31 and L33,34,35,37,41,38 and L39 also checked q47,48,49 and 51 base and emitter same wave form and strength am I doing something wrong here? maybe just some rf with no modulation? Thanks Ira
Back in the 90s, when someone brought us a Uniden-made SSB radio with a failed final we adopted the habit of asking "You didn't key it into a Palomar 300A, did you? If the answer was yes, they got told not to put it in line with that radio until the 300A got fixed.
Only had to have a couple of customers take a radio home with a new final and poof it the first day for this policy to emerge. Pretty sure this indicates one or more failed relays. That's what I blamed it on at the time. Strangely enough once the amplifier's relays were replaced the "POOF" issue would go away.
73