lake 4500 base station-tx and rx trouble

[ramblingman]

hello,i recently purchased a lake 4500-base.it is a nice looking old rig.only problem is its like the relay is sticking,but i dont think thats the deal.when you first power it up,it receives fine.then when you key the mic,it dead keys about 2 watts,and when you release the mic,it drops to about 1 watt dead key on the meter,and the receive does not come back until you turn power off.after you turn power off and then back on receive is fine again.until you key mic again.and also when it is stuck in this half tx mode,it makes a lot of static type noise.until you turn power off.turn power back on and rx is fine again.this rig has a p.c.b.,that im not at all fimaliar with,it has a ac-504 p.c.b. and the pll is a hd42851b3.and the pll is on a seperate board from main p.c.b. it is on a board slant mounted,on which the channel selector,crystals,pll i.c. .also in the back of the radio,mounted on the back rail,appears to bo an rf antennuator,with a black and a red rca jack plugs,and three other wires attached,red wire,black wire ,and white wire.it uses an ha-1339 audio chip,and a 2sc-2092 final,and a 2sc-2091 driver.it is a relay type radio,but i checked close as i key and unkey,and the relay is laching and unlaching good.

[Rick]

Check the back EMF diode.

Rick.

[ramblingman]

thanks for the info. rick,i check the diode out.i appreciate your help,my friend as always.....take care........ramblinman

[ramblingman]

i removed the diode and checked it,it checks good.i think im gonna remove the relay and take a look at it,contacts may need buffing.

[Chevin]

A relay can only stay engage if it has positive volts on one side of the coil and ground or negative on the other side. If the emf diode was faulty then it would not deactivate very quickly due to the coil ringing. Other problems you can get with relays are the reset spring can become weak. The easy way to find the fault is just try a second relay.

Chevin.

[ramblingman]

well,i removed the relay,and buffed the contacts.but no fix,its still doing the same think.will receive fine when you first power it up.then when you key mic.it dead keys 2 watts,then you release the mic it drops to about 1 watt on meter.but receive will not come back,until you turn off power,then turn back on power.another thing,i put a second test radio,beside it.and listen,when i key the lake and modulate it sounds good,thru the test radio.and when you unkey the lake,it completly unkeys on the second test radio.but not on the lake.also when you unkey the lake,it has a static sound,that also registers on s meter.only way to get it to return to normal receive,is too turn off power,and then turn back on....if anyone has any other ideas what trouble could be.id appreciate your input....so far ive checked diode,it checks good,also i checked the transistor next to relay,and it checks good,also buffed relay contacts,and it appears to be working properly...thanks for your help.........ramblinman

[Rick]

Have you tried removing one of the relay coil wires when you have the fault as per Chevin message above, at least this will tell you if it a relay fault or something else, if the relay is using a transistor to turn it on check to see if the transistor as turn off it maybe leaking or bad holding cap. A fault like this should be easy to find.

Rick.

[ramblingman]

thanks guys for the suggestions,i try checking that..i appreciate your help,rick and chevin.....ramblinman

[ramblingman]

hello once again,hope everyone is doing well today.i have about decided that im gonna need a new relay in this unit.i thought i might have a second handed one on hand,but i dont.always have everything but what you need you know////.it may be a hard to find item i dont know..it is a 16 series 4pdt relay..does anyone know where may be a good place to purchase one..ive looked at rf parts,but i cant seem to find one there...i pretty sure im gonna need one though...ive checked all the parts in accosication with the relay,,the emf diode,transistor,capacitor.they are not open or short,and the cap.is within tolerance on capacitance checker...unless the transistor is leaky,i cant determine that....if it wasnt such a nice old unit,i might just put it to the side as parts radio..but id sure like to get this one going.......thanks ramblinman

[Rick]

Hear is a list I found on the Internet in 5 minutes

www.rfparts.com/relay.html#r10

www.rfparts.com/relay.html#special

www.kenselectronics.com/lists/relays.htm

http://www.digikey.com/scripts/DkSearch ... =Relay;FV=

It maybe worth just try to hard wire any relay in to see if it works.

Rick.

[ramblingman]

hello rick,,,this might be a stupid question,,but i never claimed to be the sharpest knife in the drawer.although i am not a butter knife either...but,,,you said i could hard wire any relay in,in order to check it...how do you say go about wiring a 3pdt relay,in place where a 4pdt relay was.ive never fooled to much with relays,just either change them out,for the proper one.or either buff the contacts,sometimes is all it takes..........

[Rick]

Well as I do not have a diagram of the radio, I do not know how many contacts are been used. However, it should be easy to see which ones are being used, is the relay like the one in the Adams or Cobra 138 in which case it is a 4 pole change-over but only used 3 of the poles.

Rick.