Racal-Dana 9916 input A issue - UK Vintage Radio Repair and Restoration Discussion Forum

bbjunkie · 9th Apr 2017, 11:09 pm

Hi all,

Bought this some time ago, sold as working 3-4 years ago but due to a house move etc I am only getting around to using it now.
It had sensitivity issues with Input B which I've managed to sort by replacing Q1 (used a 2N3819) but Input A is causing a bigger problem. Unless I feed it with a +13dBm signal it fails to display the frequency.

Have traced the signal through C36 to pin 7 & 8 of RL1 but I cant see a signal coming out of the relay.

Does anyone have the technical specs of this item? I've got a schematic here that lists it as being compatible with RS 817-117 but unfortunately this is also now obsolete. RS suggest a 291-9710 as a replacement but am unsure if this will be suitable.
The schematic shows some other connections to RL1 but as I don't have a datasheet I cant tell what's meant to be going on inside.

Any thoughts?

Cheers

Pete

karesz* · 10th Apr 2017, 2:48 am

Hi Pete,
what is exact type of RL1 please?
Karl

Dickie · 10th Apr 2017, 10:37 am

Looks like a fairly generic SPNO DIL reed relay. I can't find a spec for the 9616 input A but I am guessing its the low-frequency input. The pin out given for the RS alternative should enable you to check whether the relay is faulty (by bridging pins 1-7) or else its coil drive is lacking.

PETERg0rsq · 10th Apr 2017, 11:57 am

Pete

I am presuming you mean a 9916 (as Racal did not make a 9616 as far as I am aware).

The relay is the input overload protection for the UHF input.

The relay should be energized to permit the signal through it.

Normally IC29 sinks the current through RLA1, but in an overload condition IC29 turns ON and puts an equal voltage across RLA1 coil. Q8 should light the overload lamp if this happens.

However the usual mode of failure is RLA1 to stick. A couple of sharp taps on it might free it off. Otherwise any 5V reed relay can be used to replace it.

Checking 291-9710 against the schematic, all the pins are compatible, pin 9, 10 and 13 are not connected.

Peter

bbjunkie · 10th Apr 2017, 7:32 pm

Thanks everyone for the responses. First of all, sorry yes it's the 9916 not 9616!

Input A is the 40-520MHz input. I have a feeling I may have a few separate issues here, bridging 1&7 (actually injecting the -10dBm signal at pin1) made quite a difference, was able to read a -14dBm signal.
I'll get one of the RS items ordered and go from there.

Cheers guys!
Pete

bbjunkie · 25th May 2017, 12:43 am

Hi All,

Just a quick update. Got hold of an RS Components 291-9710 and fitted it tonight. After some quick tests I think things are back to as they should be. Able to count a -41dBm signal at 10MHz and -33dBm at 520MHz

Much better!

Thanks for the tips & pointers

Pete

9th Apr 2017, 11:09 pm	#1
bbjunkie Triode Join Date: Feb 2017 Location: Lisburn, Northern Ireland, UK. Posts: 10	Racal-Dana 9916 input A issue Hi all, Bought this some time ago, sold as working 3-4 years ago but due to a house move etc I am only getting around to using it now. It had sensitivity issues with Input B which I've managed to sort by replacing Q1 (used a 2N3819) but Input A is causing a bigger problem. Unless I feed it with a +13dBm signal it fails to display the frequency. Have traced the signal through C36 to pin 7 & 8 of RL1 but I cant see a signal coming out of the relay. Does anyone have the technical specs of this item? I've got a schematic here that lists it as being compatible with RS 817-117 but unfortunately this is also now obsolete. RS suggest a 291-9710 as a replacement but am unsure if this will be suitable. The schematic shows some other connections to RL1 but as I don't have a datasheet I cant tell what's meant to be going on inside. Any thoughts? Cheers Pete

10th Apr 2017, 2:48 am	#2
karesz* Heptode Join Date: Jun 2010 Location: Zurich, Switzerland Posts: 538	Re: Racal-Dana 9616 input A issue Hi Pete, what is exact type of RL1 please? Karl

10th Apr 2017, 10:37 am	#3
Dickie Octode Join Date: Sep 2004 Location: St. Albans, Hertfordshire, UK. Posts: 1,478	Re: Racal-Dana 9616 input A issue Looks like a fairly generic SPNO DIL reed relay. I can't find a spec for the 9616 input A but I am guessing its the low-frequency input. The pin out given for the RS alternative should enable you to check whether the relay is faulty (by bridging pins 1-7) or else its coil drive is lacking. __________________ Regards, Richard, BVWS member

10th Apr 2017, 11:57 am	#4
PETERg0rsq Heptode Join Date: Jun 2009 Location: St Helens, Lancashire, UK. Posts: 641	Re: Racal-Dana 9616 input A issue Pete I am presuming you mean a 9916 (as Racal did not make a 9616 as far as I am aware). The relay is the input overload protection for the UHF input. The relay should be energized to permit the signal through it. Normally IC29 sinks the current through RLA1, but in an overload condition IC29 turns ON and puts an equal voltage across RLA1 coil. Q8 should light the overload lamp if this happens. However the usual mode of failure is RLA1 to stick. A couple of sharp taps on it might free it off. Otherwise any 5V reed relay can be used to replace it. Checking 291-9710 against the schematic, all the pins are compatible, pin 9, 10 and 13 are not connected. Peter __________________ SPECIALIST.....Knows everything about nothing EXPERT..........Knows nothing about everything

10th Apr 2017, 7:32 pm	#5
bbjunkie Triode Join Date: Feb 2017 Location: Lisburn, Northern Ireland, UK. Posts: 10	Re: Racal-Dana 9616 input A issue Thanks everyone for the responses. First of all, sorry yes it's the 9916 not 9616! Input A is the 40-520MHz input. I have a feeling I may have a few separate issues here, bridging 1&7 (actually injecting the -10dBm signal at pin1) made quite a difference, was able to read a -14dBm signal. I'll get one of the RS items ordered and go from there. Cheers guys! Pete

25th May 2017, 12:43 am	#6
bbjunkie Triode Join Date: Feb 2017 Location: Lisburn, Northern Ireland, UK. Posts: 10	Re: Racal-Dana 9916 input A issue Hi All, Just a quick update. Got hold of an RS Components 291-9710 and fitted it tonight. After some quick tests I think things are back to as they should be. Able to count a -41dBm signal at 10MHz and -33dBm at 520MHz Much better! Thanks for the tips & pointers Pete