Retune Harris DX10

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DX10-Tandag
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Retune Harris DX10

Post by DX10-Tandag » Tue Sep 18, 2018 4:58 pm

Has anybody here has done retuning a Harris DX10?

The situation is like this... we have an old SENDER 10kW transmitter that had been put out of service due unavailability of spare parts. We were able to acquire an old Harris DX10 from another station but it was tuned to a different frequency from what we are authorized to use. I tried to find a solution from its operations manual but find it hard to configure.

Thanks..

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Deep Thought
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Re: Retune Harris DX10

Post by Deep Thought » Tue Sep 18, 2018 5:56 pm

What frequency is it on and what frequency do you need it tuned to?

It is possible to do it but you'll need the proper test equipment and possibly some replacement parts.
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

RodeoJack
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Re: Retune Harris DX10

Post by RodeoJack » Wed Sep 19, 2018 9:18 am

So... the hint here is whether you've ever tackled a project like this before. If not, you should start by finding someone who has, to either work with or take the project on. Not that the qualifications aren't here, but I think the job is beyond anyone here being able to walk you through it over the discussion board... unless you both have 6 months worth of time.

If DT doesn't have the document information you need, I probably do. Also... while they're confused about what AM still means to them, there still are a couple of guys at Gatesair, who know the transmitter and (maybe) can still send you the documentation you need.

There are two or three revisions to this transmitter. The serial number and/or manufacture date will determine the parts chart they think you should use. Some of that was due to them needing to adjust the transmitter's NRSC performance, or so they say. There are also a couple of revisions to the boards in the center section that you'll need to look into before starting. The boards don't look all that different, but Harris changed the part numbers, making it difficult to adjust them if you don't have the right docs.

If you don't already have the information and do take the opportunity to call Gatesair, ask them for a copy of your transmitter's original test sheet. That will give you some reference numbers to shoot for.

Assuming everything else about the transmitter is OK, you're looking at a crystal change and probably the replacement of a number of capacitors. The scope of that depends on how far you're moving the transmitter frequency from where it's set now. That info is in the charts.

If you're moving the frequency a bunch, you may be faced with changing the transmitter's bandpass filter capacitor. This is a big variable cap in the middle of the left cabinet that, by itself, can cost you somewhere between $2,000 and $6,000, give or take. I got mine from a surplus shop. Gatesair has (or can get) them. That route will get you the high price. The number, type and configuration of the other large caps in that section, as well as some smaller ones in the PA cabinet may also need to be changed. Gatesair has changed the specs in this area as well, so as to deal with parts availability and performance issues (again... so they say).

The outfit that made the crystals for that transmitter is gone now, so you'll need to find an alternative. See this: viewtopic.php?f=2&t=6498
for some idea where you might be headed.

As DT says, you'll need some test gear to do the tune up, and it would help if you have some background in this area... not that it's that difficult, but it can get that way if it's your first try at it. At best, it will take time and plenty of patience. Again... if you don't have that gear and/or it's your first attempt, it would be well within your best interest to find an engineer with experience at this to work with. Pretty much all of the larger inductors and about 60% of the parts with knobs, switches or a screwdriver slot will get adjusted, one way or the other.

Opinions differ, but I think the DX-10 is probably one of the oldest series of transmitter still worth making a change like this... at least it was, before the crystal issue. If you get it right and can find the parts without breaking your wallet, the transmitter will sit there and sing like a bird for a long time. However, it's getting to the point where that decision is really in the balance, cost-wise.

You might also want to evaluate the capacitors in the power supply and PA sections (service bulletin on this for the DX, SX and Gates series of transmitters. If those haven't been replaced in 10 years or so of use, you might be looking at that job as well. Depending on source, figure upwards of another couple thousand for parts and another half-day's work, +/-, if you need a full set.

If all fails, and a new transmitter is in your future, Nautel is about the only company left standing, so far as a seriously reliable box of that size is concerned. Broadcast Electronics makes a 10kW unit, but every one I've been around seems to be pushing too hard at full power. Also, the power supply boards (which are usually what fails), are stuffed into the available space and you need to be a contortionist to get to them.
Last edited by RodeoJack on Wed Sep 19, 2018 9:40 am, edited 3 times in total.

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Deep Thought
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Re: Retune Harris DX10

Post by Deep Thought » Wed Sep 19, 2018 9:37 am

Data point: As of about two months ago Nautel was selling their current-production NX-10 for about $42,000 "street price". This box includes MDCL as a standard feature which can meaningfully reduce your electric bill.

While that is probably considerably more than you have invested in the DX-10 it may be worth considering since it gets you a transmitter that was designed in the 2010s rather than the 1980s.
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Scott.Cason
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Re: Retune Harris DX10

Post by Scott.Cason » Thu Sep 20, 2018 1:07 pm

and will be a hell of a lot more efficient than the Harris, and won't need to be replaced in another 10 years.
Deep Thought wrote:
Wed Sep 19, 2018 9:37 am
Data point: As of about two months ago Nautel was selling their current-production NX-10 for about $42,000 "street price". This box includes MDCL as a standard feature which can meaningfully reduce your electric bill.

While that is probably considerably more than you have invested in the DX-10 it may be worth considering since it gets you a transmitter that was designed in the 2010s rather than the 1980s.
LaGrange Communications - http://www.lagrange-com.com
Froggy 95.9 - http://froggy959.net/

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kkiddkkidd
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Re: Retune Harris DX10

Post by kkiddkkidd » Fri Sep 21, 2018 8:09 am

Scott.Cason wrote:
Thu Sep 20, 2018 1:07 pm
and will be a hell of a lot more efficient than the Harris, and won't need to be replaced in another 10 years.
I'm curious if anyone has replaced something like a DX10 or SX-? with a new Nautel or other transmitter and observed a significant increase in efficiency? I actually would have though that the efficiency would be reasonably close (not withstanding MDCL) but have never had occasion to replace a SS TX with another SS TX.

Later,
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sallen
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Re: Retune Harris DX10

Post by sallen » Fri Sep 21, 2018 8:30 am

There is no driver section or pre drive amps in a Nautel NX series. So no power needed for this intermediate stage. Just replaced a ND50 (is now backup) with a NX50. There was a little decrease in the power bill. Not using MDCL yet at this station, but the preset is set up to do it.

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kkiddkkidd
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Re: Retune Harris DX10

Post by kkiddkkidd » Fri Sep 21, 2018 9:14 am

sallen wrote:
Fri Sep 21, 2018 8:30 am
There is no driver section or pre drive amps in a Nautel NX series. So no power needed for this intermediate stage. Just replaced a ND50 (is now backup) with a NX50. There was a little decrease in the power bill. Not using MDCL yet at this station, but the preset is set up to do it.
I had not considered that.

Nor do they have all those little flickering lamps in a MW... It sounds odd but I have never much more than opened the door on an MW. Middle TN and N. Alabama skipped that generation and the first SS TX's that appeared here were the SX's and BE AM series and most of them are still in service.
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Kevin C. Kidd CSRE/AMD
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