You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
The Feb 2025 Radioddity Giveaway Results are In! Click Here to see who won!

Reply to thread

Message

I won't get around to removing the cover and taking pictures until later next week.
I have a very strong suspicion that you are absolutely correct in assuming the issue is being caused by the preamplifier section in the 300a
A curious thing happened
As I mentioned in my previous post, the preamplifier on this 300al hasn't worked in years. I'm sure you know what happens when the preamps in these amplifiers goes south. They actually D amplifier when switched in the pre amplification mode.
I decided to put the switch in the pre amplification position. Lo and behold the preamplifier actually works! I didn't have enough time to run the radio and amplifier with the switch for the preamp in that position for a long. so I don't know what exactly will happen when I do use it for an hour or so. I did get a chance to have a couple of short qso's with a few locals and during those conversations the preamp did exactly as it's supposed to. The odd thing about it is when I switched the preamp into the off position it did as if I switched it in the on position when it wasn't operational and D Amplified everyone signal. I flipped it up and down a few times rapidly thinking I'd possibly do something positive by doing so. Shows you how much I know! Anyway, the deal with it now is if I leave the preamplifier switch in the on position it works and amplifies everyone signal as if it was never busted. Believe me when I tell you this preamplifier hasn't worked since 1980. I haven't opened the cover or done anything to the amplifier that would change the way it was working or in this case not working. I guess I will wait until next week when I remove the cover and take some photos. Depending on which configuration of relays this particular 300 a has depends on (I guess) whether it can be repaired or even if it's worth it. As of last evening with the pre amplification switch in the on position the receive did not drop out and the amp just seemed as if it was working properly as far as the preamplifier goes. I am fairly positive that this is not going to last. There is obviously an issue with the preamplifier on this 300a, and it's an issue that makes it annoying enough to either have it repaired or to boxing it up and relegate it to the closet with the rest of the retired equipment. I do have other choices. there's one reason why I like using this amplifier with the sonar 2340. The 2340 with the Demco modulator turned up to approximately 3 gives me nice loud yet clear audio with little to no background noise from the amplifiers fan. It is truly one of the quietest fans of any amplifier I own. I once was using the Phantom with the 2340 but with that fan noise I could only turn the Demco modulator up to approximately 11. It still sounded nice with the modulator at 11 but I get much louder reports with the Demco at 3 o'clock. It's impossible to leave the Demco at 3 while using the Phantom. At 3 o'clock on the Demco with the Phantom my dead key reeds 300 watts (150 watts of fan noise). Compared to the 300 a which theres practically no background noise and dead keys a solid quiet 150 watts. With the Demco at zero (no audio) I get 145 DK. That's 5 watts of fan noise. No one I've asked says they hear any fan on a quiet Dead cake while I use the 300 a. The Phantom sounds like a jet engine taking off. The difference between the fan noise is night and day. This is really the only reason why I use the 300a with the sonar and Demco modulator. I would love to fix the 300a but considering it's something I wouldn't be able to do on my own and would have to pay to have it done sadly means it most likely will become a closet case. It's going to cost me $60 to ship it round trip. Then probably around 60 to $100 to repair. It's really not a lot of money but it's not worth it considering I do have other options. I hope that you (nomad) can possibly guide me through the repair. And even though I'm skeptical of being able to fix it on my own, I am willing to give it a try. The choices are fairly simple. Trying to fix it myself or put it in the closet where it will most likely stay until I can find a use for it. I do appreciate all the help. 73

<blockquote data-quote="Sonar" data-source="post: 594676" data-attributes="member: 47153">I won&#039;t get around to removing the cover and taking pictures until later next week.I have a very strong suspicion that you are absolutely correct in assuming the issue is being caused by the preamplifier section in the 300aA curious thing happenedAs I mentioned in my previous post, the preamplifier on this 300al hasn&#039;t worked in years. I&#039;m sure you know what happens when the preamps in these amplifiers goes south. They actually D amplifier when switched in the pre amplification mode.I decided to put the switch in the pre amplification position. Lo and behold the preamplifier actually works! I didn&#039;t have enough time to run the radio and amplifier with the switch for the preamp in that position for a long. so I don&#039;t know what exactly will happen when I do use it for an hour or so. I did get a chance to have a couple of short qso&#039;s with a few locals and during those conversations the preamp did exactly as it&#039;s supposed to. The odd thing about it is when I switched the preamp into the off position it did as if I switched it in the on position when it wasn&#039;t operational and D Amplified everyone signal. I flipped it up and down a few times rapidly thinking I&#039;d possibly do something positive by doing so. Shows you how much I know! Anyway, the deal with it now is if I leave the preamplifier switch in the on position it works and amplifies everyone signal as if it was never busted. Believe me when I tell you this preamplifier hasn&#039;t worked since 1980. I haven&#039;t opened the cover or done anything to the amplifier that would change the way it was working or in this case not working. I guess I will wait until next week when I remove the cover and take some photos. Depending on which configuration of relays this particular 300 a has depends on (I guess) whether it can be repaired or even if it&#039;s worth it. As of last evening with the pre amplification switch in the on position the receive did not drop out and the amp just seemed as if it was working properly as far as the preamplifier goes. I am fairly positive that this is not going to last. There is obviously an issue with the preamplifier on this 300a, and it&#039;s an issue that makes it annoying enough to either have it repaired or to boxing it up and relegate it to the closet with the rest of the retired equipment. I do have other choices. there&#039;s one reason why I like using this amplifier with the sonar 2340. The 2340 with the Demco modulator turned up to approximately 3 gives me nice loud yet clear audio with little to no background noise from the amplifiers fan. It is truly one of the quietest fans of any amplifier I own. I once was using the Phantom with the 2340 but with that fan noise I could only turn the Demco modulator up to approximately 11. It still sounded nice with the modulator at 11 but I get much louder reports with the Demco at 3 o&#039;clock. It&#039;s impossible to leave the Demco at 3 while using the Phantom. At 3 o&#039;clock on the Demco with the Phantom my dead key reeds 300 watts (150 watts of fan noise). Compared to the 300 a which theres practically no background noise and dead keys a solid quiet 150 watts. With the Demco at zero (no audio) I get 145 DK. That&#039;s 5 watts of fan noise. No one I&#039;ve asked says they hear any fan on a quiet Dead cake while I use the 300 a. The Phantom sounds like a jet engine taking off. The difference between the fan noise is night and day. This is really the only reason why I use the 300a with the sonar and Demco modulator. I would love to fix the 300a but considering it&#039;s something I wouldn&#039;t be able to do on my own and would have to pay to have it done sadly means it most likely will become a closet case. It&#039;s going to cost me $60 to ship it round trip. Then probably around 60 to $100 to repair. It&#039;s really not a lot of money but it&#039;s not worth it considering I do have other options. I hope that you (nomad) can possibly guide me through the repair. And even though I&#039;m skeptical of being able to fix it on my own, I am willing to give it a try. The choices are fairly simple. Trying to fix it myself or put it in the closet where it will most likely stay until I can find a use for it. I do appreciate all the help. 73</blockquote>

[QUOTE="Sonar, post: 594676, member: 47153"] I won't get around to removing the cover and taking pictures until later next week. I have a very strong suspicion that you are absolutely correct in assuming the issue is being caused by the preamplifier section in the 300a A curious thing happened As I mentioned in my previous post, the preamplifier on this 300al hasn't worked in years. I'm sure you know what happens when the preamps in these amplifiers goes south. They actually D amplifier when switched in the pre amplification mode. I decided to put the switch in the pre amplification position. Lo and behold the preamplifier actually works! I didn't have enough time to run the radio and amplifier with the switch for the preamp in that position for a long. so I don't know what exactly will happen when I do use it for an hour or so. I did get a chance to have a couple of short qso's with a few locals and during those conversations the preamp did exactly as it's supposed to. The odd thing about it is when I switched the preamp into the off position it did as if I switched it in the on position when it wasn't operational and D Amplified everyone signal. I flipped it up and down a few times rapidly thinking I'd possibly do something positive by doing so. Shows you how much I know! Anyway, the deal with it now is if I leave the preamplifier switch in the on position it works and amplifies everyone signal as if it was never busted. Believe me when I tell you this preamplifier hasn't worked since 1980. I haven't opened the cover or done anything to the amplifier that would change the way it was working or in this case not working. I guess I will wait until next week when I remove the cover and take some photos. Depending on which configuration of relays this particular 300 a has depends on (I guess) whether it can be repaired or even if it's worth it. As of last evening with the pre amplification switch in the on position the receive did not drop out and the amp just seemed as if it was working properly as far as the preamplifier goes. I am fairly positive that this is not going to last. There is obviously an issue with the preamplifier on this 300a, and it's an issue that makes it annoying enough to either have it repaired or to boxing it up and relegate it to the closet with the rest of the retired equipment. I do have other choices. there's one reason why I like using this amplifier with the sonar 2340. The 2340 with the Demco modulator turned up to approximately 3 gives me nice loud yet clear audio with little to no background noise from the amplifiers fan. It is truly one of the quietest fans of any amplifier I own. I once was using the Phantom with the 2340 but with that fan noise I could only turn the Demco modulator up to approximately 11. It still sounded nice with the modulator at 11 but I get much louder reports with the Demco at 3 o'clock. It's impossible to leave the Demco at 3 while using the Phantom. At 3 o'clock on the Demco with the Phantom my dead key reeds 300 watts (150 watts of fan noise). Compared to the 300 a which theres practically no background noise and dead keys a solid quiet 150 watts. With the Demco at zero (no audio) I get 145 DK. That's 5 watts of fan noise. No one I've asked says they hear any fan on a quiet Dead cake while I use the 300 a. The Phantom sounds like a jet engine taking off. The difference between the fan noise is night and day. This is really the only reason why I use the 300a with the sonar and Demco modulator. I would love to fix the 300a but considering it's something I wouldn't be able to do on my own and would have to pay to have it done sadly means it most likely will become a closet case. It's going to cost me $60 to ship it round trip. Then probably around 60 to $100 to repair. It's really not a lot of money but it's not worth it considering I do have other options. I hope that you (nomad) can possibly guide me through the repair. And even though I'm skeptical of being able to fix it on my own, I am willing to give it a try. The choices are fairly simple. Trying to fix it myself or put it in the closet where it will most likely stay until I can find a use for it. I do appreciate all the help. 73 [/QUOTE]

Top Bottom