Stridsberg MCA208M Multi-Coupler Burnout?

[TailGator911]

I have been troubleshooting major problem this morning (new R8600 went totally deaf on vhf/uhf during test) and narrowed it down to my Stridsberg MCA208M 8-way multi-coupler that feeds 8 scanners from Diamond discone antenna on roof. I have been shuffling ports around the last couple of days to include the R8600 onto the discone for vhf/uhf/800mhz coverage and making the last port on 8-way available for SDS200 (as well as 4-port). While doing comparison tests between R8600 and SDS100, the r8600 fed thru m/c from discone, sds100 thru 4-port SD from directional yagi, the R8600 went dead. Hooked SDS100 to same port on 8-way and nada. All other scanners on 8-port dead in the water. Took mainline direct to SDS100/R8600 and other scanners - there it wasn't, no signal whatsoever coming from MCA208M!! I always make it a point to power down scanners when changing antenna feeds/couplers, so I am wondering if I caused this by connecting/disconnecting so many times in the last few days? Static discharge? AC is good, antennas are grounded, but multi-coupler is not singularly grounded. Any ideas what happened? If I remember right, I paid almost $350 for this in 2014. I am searching internet for similar instances but only found one post by air traffic controller that some chip inside had burnt out (again). I think I bought my 4-port for the yagi from ScannerMaster, but the 8-port for the disconeI bought from DX Engineering. I am sure it is out of warranty. Will be on the phone with them in the morning. I feel like I did something wrong getting in there and switching lines around, twisting those BNCs so many times. Any ideas?

JD
kf4anc

 

[Ubbe]

I assume the green LED shows that you have power so it must be the amplifier transistor that's gone bad. If you can solder you can exchange that transistor yourself and save the shipping cost. Open up the combiner and take a look, maybe there's a lead that came loose while you handled the combiner. Stridsberg often have reasonable repair charges but getting the transistor from them are even less costly.

/Ubbe

 

[autovon]

Send it in, they'll fix it. Same thing happened to my 8 port. One day it worked and the next day it didn't. No changes to the station, no transmitters nearby, no lightning, etc.

 

[mancow]

I tried figuring out what transistor they use but haven't had any luck yet. I can't recall the marking now but it was something like x4 and that's it.

 

[prcguy]

Its probably a four lead broad band RF amp IC.

I tried figuring out what transistor they use but haven't had any luck yet. I can't recall the marking now but it was something like x4 and that's it.

 

[mancow]

Yes it's a 4 lead. I will look again at the part marking when I get time.

 

[prcguy]

It would be real nice to get the right part #, not only to repair these but to know its gain, NF and compression points.

Yes it's a 4 lead. I will look again at the part marking when I get time.

 

[TailGator911]

Thanks for the replies, guys. I am a marginal solderer, can do my own Pl-259s, change out resistors, etc. Do basic troubleshooting down to component level. Never replaced an internal amp or transistor, but my eyes are not so sharp anymore and hands tend to shake sometimes due to health issues so it's a no- brainer for me send it in and do without for a bit. Get it done right. I will be contacting Stridsberg in the AM. Nice to know I didn't blow it up switching leads and all. Thanks again

JD
kf4anc

 

[N9JIG]

There is a protection diode that pops in case of too much RF going into the unit, they would pop in my truck due to my dual band ham rig antenna being too close. If this is the case with yours Stridsberg will repair it under warranty (if within the time period) and even if it isn't under warranty the repair is not that steep.

 

[mule1075]

There is a protection diode that pops in case of too much RF going into the unit, they would pop in my truck due to my dual band ham rig antenna being too close. If this is the case with yours Stridsberg will repair it under warranty (if within the time period) and even if it isn't under warranty the repair is not that steep.

$45 is what I paid for repair plus whatever it cost to ship it. Turnaround time was about a week.

 

[TailGator911]

$45 is what I paid for repair plus whatever it cost to ship it. Turnaround time was about a week.

Yup, after some early morning scanner excitement, made the call, mailed the Stridsberg in, then came home to nice little pkg on front porch. New SDS200 to play with! I think I will be somewhat preoccupied for the next week or so

Thanks guys!

JD
kf4anc

 

[prcguy]

Looking through the MiniCircuits catalog it looks like the ERA-6SM+ might be a contender for a replacement MMIC. If the overall gain of an 8-way Stridesberg is about 2dB then the internal amp would have about 10dB gain. They don't specify the noise figure but its probably not great considering the IP1 rating of the multicoupler as the amp would be out of the low noise category and into the higher power line driver type. The IP1-IP3 rating of the Stridesbergs are not really that special.

I think you could buy a power divider and amp from MiniCircuits, all connectorized, and have a higher spec multicoupler than the Stridesberg for less $$.

 

[mancow]

It's marked 4x.

 

[TailGator911]

I have used Stridsbergs for years and this is the first hiccup ever, and they were really very polite and professional on the phone. I really think it was something I did when switching around all the leads when I was vhf/uhf comparing R8600 and SDS100, maybe a touch of static or something, who knows. I will definitely bookmark your suggestion for future radio reference if needed tho! Thanks man

JD
kf4anc

 

[KevinC]

You may have a potential difference between two (or more) of your radio chassis, which took out the amp as you switched cables around.

 

[prcguy]

It doesn't sound like you did anything that would damage the Stridesberg, there should be no static problems at the BNC connectors since the shield contacts first and the power input is heavily bypassed. A difference in potential between radios and their antenna cables should only cause a little current to flow on the coax shields to equalize the potential, and the shield of the BNC makes contact well before the center pin.

I have used Stridsbergs for years and this is the first hiccup ever, and they were really very polite and professional on the phone. I really think it was something I did when switching around all the leads when I was vhf/uhf comparing R8600 and SDS100, maybe a touch of static or something, who knows. I will definitely bookmark your suggestion for future radio reference if needed tho! Thanks man

JD
kf4anc

 

[TailGator911]

You may have a potential difference between two (or more) of your radio chassis, which took out the amp as you switched cables around.

Ah, sounds plausible there. I have probably been overthinking it. Makes me want to handle those pigtails with kid gloves

 

[pro92b]

It's marked 4x.

Mini-Circuits
https://www.minicircuits.com/app/AN60-028.pdf

 

[buddrousa]

Ah, sounds plausible there. I have probably been overthinking it. Makes me want to handle those pigtails with kid gloves

Did you get your stridsberg back yet?

 

[TailGator911]

They actually sent me a brand new one, no reason given, so I was totally satisfied with their customer service. I am confusing another repair issue. They sent me a new one, I did not pay for repair. Quick turnaround. They are the best. I dealt with an older guy there, a ham, I think his name was John? Not sure, but he was a talker. Great guy, great service!

JD
kf4anc