FL2100B attentuating receive

[VE3TMT]

Greetings,

About a month ago I pulled the loud stock relay out of the amp and replaced it with a couple of signal relays. All was working fine, but then about a day later I noticed when I flipped on the "OPERATE" switch, the receive n the radio would drop significantly. I have since put the original relay back in and all is fine again, but really want to switch it back out. The new relays were so quiet you would think it was a solid state amp.

Anyone know what would cause this?

 

[Captain Kilowatt]

Is the amp relay pulling in and actually switching the amp inline in RX mode? This would in effect open the receive line and account for the drop in signal.

 

[VE3TMT]

Is the amp relay pulling in and actually switching the amp inline in RX mode? This would in effect open the receive line and account for the drop in signal.

Amp works normal only keying when I key the radio. No plate current on meter in receive so the TX is not kicking in. Only receive signal drops.

VE3TMT

 

[wavrider]

contacts in relay are not making a good contact or relay is keying in receive,

Not to much else it could be.

Simple continuity check on the relay should verify what the problem is

 

[VE3TMT]

contacts in relay are not making a good contact or relay is keying in receive,

Not to much else it could be.

Simple continuity check on the relay should verify what the problem is

The relays were brand new. May attempt to reinstall. Just want to nail down issue first.

 

[Captain Kilowatt]

Amp works normal only keying when I key the radio. No plate current on meter in receive so the TX is not kicking in. Only receive signal drops.

VE3TMT

You have two separate relays in the RX path. One relay may be pulling in as soon as you turn it on and is opening the RX path. As soon as you key the amp the other relay operates normally and the amp appears to function normally. This is what could be happening. Also check your RX/STD.BY switch and the PTT line to the exciter.

 

[VE3TMT]

You have two separate relays in the RX path. One relay may be pulling in as soon as you turn it on and is opening the RX path. As soon as you key the amp the other relay operates normally and the amp appears to function normally. This is what could be happening. Also check your RX/STD.BY switch and the PTT line to the exciter.

I replaced the relays with a couple of TE Connectivity units (DigiKey Part # PB968-ND) and all seems to be working fine. I used two DPDT relays, and each relay has the contacts bridged to double the current capacity. This will give me a total of 16A capacity per set of contacts, where the original Yaesu relay was only rated 10A. I also moved the filament center-tap resistor (another mod) to a separate relay. I think this may have been the source of the problem in the beginning. The amp is much quieter now when keying.

Merry Christmas and Happy New Year to all!

Max, VE3TMT

 

[Shockwave]

I think you'll find you have welded one set of contacts together in the last relays you changed out. It's not just the amps you have to be concerned about here. That relay is subject to "hot switching" and develops an arc on the output contact when this happens due to the high RF voltage across the contacts. Part of this relates to the voltage rating of the contacts but it's also effected by the return tension of the spring used in the relay. Weak springs allow a rather small arc to hold the contacts together after coil voltage is removed.

 

[VE3TMT]

I think you'll find you have welded one set of contacts together in the last relays you changed out. It's not just the amps you have to be concerned about here. That relay is subject to "hot switching" and develops an arc on the output contact when this happens due to the high RF voltage across the contacts. Part of this relates to the voltage rating of the contacts but it's also effected by the return tension of the spring used in the relay. Weak springs allow a rather small arc to hold the contacts together after coil voltage is removed.

If the contacts were welded shut the receive would have been full strength. This would have shorted the RF IN and RF OUT connections together. I'm thinking I may have burned out a set of contacts, not allowing the receive path to close. I have had no problems since putting in new higher current rated relays a week ago. It makes the FL2100B a whole new amp. Now if I could just get rid of the slight transformer hum!