Changing the Capacitors in a DX-50

This lovely transmitter is 33 years old! I thought we’d celebrate by changing the electrolytic capacitors! It appears that some of the capacitors were changed in 2009, but many are original to the transmitter. Gates Air recommends replacing the electrolytic capacitors during the course of regular maintenance cycles. Dried-out capacitors can lead to a variety of mysterious fault conditions including low drive levels, poor audio quality, difficulty starting the transmitter, and so on. See Harris service bulletin AM-579-JK.

DX-50 transmitter

Some of the Low Voltage Power Supply capacitors were at least partly dried out. They felt a little bit light and one of them rattled when I shook it.

Replacing large PA capacitors

Gates Air has a full replacement kit, part number 973-2100-391. When I looked into it, the price of this kit is very reasonable and is closely aligned with the prices from Mouser Electronics.

Old capacitors for disposal

Here is a full list of capacitors needed, I put the Mouser part numbers in just in case:

NomenclatureAmountGates Air PNMouser PN
Cap, 5,100 uf 350 V17524-0341-000598-DCM512T350DG2A
Cap, 5,500 uf 200 V4524-0219-000
Cap, 15,000 uf 100 v2524-0322-000
Cap, 76,000 uf 40 v4524-0342-000
Cap, 120,000 uf 40 V*2524-0380-00075-36DX124G040DJ2A
Large Capacitors for DX-50 transmitter

*See Harris service bulletin AM-474-TLH for information on the -8 volt power supply.

Board is green, Returned to service

Most of the capacitors in the PA section were original to the transmitter, as well as those in the 30-volt and 60-volt driver supply.

One important detail; pay attention when installing these things. You do not want to reverse the polarity on an electrolytic capacitor, it will likely explode. These units are pretty big and the explosion would be loud and messy.

With that done, I also went through the transmitter and reset all of the voltage levels according to the factory test data sheet. When it was returned to the air, it sounded great!

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5 thoughts on “Changing the Capacitors in a DX-50”

  1. DX-50 installed Fall 1993.
    February 1996 main transformer fire when 8 of the 12 secondary fuses blew.
    About $14k repairs.
    Harris came out to proof mods to the power supply protection circuits.
    You probably saw the Safety Bulletins about it.
    Ours was the second DX50 to lose that transformer in a short period..

    October ~ December 2006 Harris installed updated boards:
    Oscillator, DSP Mod Encoder, Controller, & Output Monitor.
    We did the full blue capacitor replacement. Many rattled. A few had their terminals eaten off.
    Mods for and HD on the air February 2007

    HD off for good 2010 when then Harris Deathstar “scientific experiment” (their words) failed..

    July 2016 MDCL installed. $4,100 rebate from Idaho Power Company for a power saving device that gained 25% or better results. We got 28% by their records. Paid for itself in 4 months.

    May 2019 Complete blue capacitor replacements. Many lighter but no rattles.

  2. Nice work Paul, very reliable transmitters the DX 50.
    Are the Nautel transmitters still at that site?
    If i recall back in the day the Nautel was used to back up the two DX 50’s and i think at the time it was a backup site for 1050 ESPN radio
    I had visited that site a few times.
    Ed Butler

  3. Bill, these transmitters have had most of those modifications done for the same reasons. I don’t know when the HD was turned off, but it was quite some time ago. MDCL (I think Harris called it AMC) was added at some point too.

    Ed, There is one Nautel used as a backup, the other one was moved to the 1050 site down the road.

  4. Nice work Paul!
    We replaced all the capacitors for the DX50 when the TX reported Powersupply fault (when deep modulation). These power filter capacitors are relatively easy to buy, and the price is not very expensive. Have you replaced the output capacitors? Ex: CAP 2400 PF 12Kv , CAP 1000 PF 20Kv …. If you know of a place that sells it please let us know

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