Re: [Drakelist] TR7 high pitched wine in audio
Jim, Great leads. Thank you. It sounds to the ear like the problem may be exactly what you are suggesting. I’ve been sorting out a few issues with the rig and only two remain – the whine, and my RIT is way off. I pulled DR7 last night for access to the RIT alignment pot, and while I don’t yet have an extender set, I took a few blind shots at getting the RIT at least into a useable range. No luck. Seems to be out of range of the pot, suggesting a broader alignment issue. I rarely use RIT, so this problem can be addressed later. The whine is more of an issue. I really like the radio and have been enjoying 60 mtr. QSO’s with my brother, Guy, in Memphis, WD5ACP; I’m near New Orleans. My brother and I have been hamming since the late 70’s and my recent Drake adventures have motivated him. He’s now awaiting receipt of a TR-7. Once these minor issues are dealt with my rig will be 100%. The only real problem I had with the rig was transmitter instability, which cleared with a cleaning of the ALC pot and a pot on the pre-driver board. I’ve been comparing the receive performance to a Ten Tec Pegasus, known to have a great receiver. The TR7 holds its own. After this I’m moving on to get my TR4CW into top shape. Thanks again. From: Jim Shorney jshor...@inebraska.com To: drakelist@zerobeat.net drakelist@zerobeat.net Sent: Monday, January 20, 2014 10:30 PM Subject: Re: [Drakelist] TR7 high pitched wine in audio The first thing I would look at is the filter cap on the DC-DC converter (Power Supply) board in the front right corner of the radio. This capacitor is IMO an always replace for any TR-7. Strange things can happen when it starts to fail, and on a rig that old it most likely is. Replace with a part specified for 105C temperature if possible. There was also an engineering change to add a 470uF axial cap to the +10v rail. This was added by Drake service to any radio that did not have it. Look for it on the bottom side of the chassis, between pins 10 (+10V) and pin 3 (ground) of the DC-DC coverter board connector. 73 -Jim NU0C On Mon, 20 Jan 2014 20:04:55 -0800 (PST), Leon Zebrick wrote: Picked up an early Sr# TR7. It's fine except for a high pitched noise in the audio. It's continuous and not affected by volume control. Not on transmit signal. It's not loud, but noticeable and annoying in headphones. Sounds like one of the oscillators is getting into the audio circuit. Any decoupling mods or improvements related to this? Sr no. Is in the 600 range. Wonder if this is something Drake eventually improved on. Or do I have a problem? Thanks. -- “There’s something out of place – let’s go and poke it with a stick.” – The Doctor, Amy’s Choice ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] TR7 high pitched wine in audio
Leon, Replace the 1000 ufd capacitor on the right forward edge of the DR-7 board. Its C9026 on the schematic. I have had this happen to one of my TR-7’s. 73, Gary http://home.roadrunner.com/~w8pu R-4A T4-X R-4B T4-XB R-4C T4-XC MS-4 L-4B RCS-4 2A 2B 2C 2NT 2CQ 2AS 4-LF TR-4 TR-4C TR-4CW/RIT RV-4C MC-4 TR-7 RV-7 CW-75 MS-7 WH-7 W-4 WV-4 MN-2700 MN-4C MN-2000 UV-3 PS-3 TR-22C TR-33C AA-10 AC-10 MMK-22 TR-6 PRN1000 ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] TR7 high pitched wine in audio
Leon, A properly working TR-7 is a joy to operate. Replace the cap Gary Poland recommended as well; although I haven't had a bad one, it can't hurt either. You may indeed have an alignment problem with the RIT. A touch-up of the frequency alignments should be done regardless. If that doesn't fix it, look at the analog switch IC on the parent board. There should be a hole in the parent board to access the RIT adjustment pot from the bottom. The very oldest may not have had it. Plan on doing a fixed passband alignment any time you remove the DR-7 or do anything else around that front right corner. Those pots are easy to bump without even realising it. There's lots of info on the internet. Google can be your friend. Get the Drakemod document, it's a good read. Ignore all advice to reverse the direction of the fan from what Drake intended, it really does work best that way. 73 -Jim NU0C On Tue, 21 Jan 2014 06:47:53 -0800 (PST), Leon Zebrick wrote: Jim, Great leads. Thank you. It sounds to the ear like the problem may be exactly what you are suggesting. Iâve been sorting out a few issues with the rig and only two remain â the whine, and my RIT is way off. I pulled DR7 last night for access to the RIT alignment pot, and while I donât yet have an extender set, I took a few blind shots at getting the RIT at least into a useable range. No luck. Seems to be out of range of the pot, suggesting a broader alignment issue. I rarely use RIT, so this problem can be addressed later. The whine is more of an issue. I really like the radio and have been enjoying 60 mtr. QSOâs with my brother, Guy, in Memphis, WD5ACP; Iâm near New Orleans. My brother and I have been hamming since the late 70âs and my recent Drake adventures have motivated him. Heâs now awaiting receipt of a TR-7. Once these minor issues are dealt with my rig will be 100%. The only real problem I had with the rig was transmitter instability, which cleared with a cleaning of the ALC pot and a pot on the pre-driver board. Iâve been comparing the receive performance to a Ten Tec Pegasus, known to have a great receiver. The TR7 holds its own. After this Iâm moving on to get my TR4CW into top shape. Thanks again. -- Ham Radio NU0C Lincoln, Nebraska, U.S.S.A. TR7/RV7/R7A/L7, TR6/RV6, T4XC/R4C/L4B, NCL2000, SB104A, R390A, GT550A/RV550A, HyGain 3750, IBM PS/2 - all vintage, all the time! Give a man a URL, and he will learn for an hour; teach him to Google, and he will learn for a lifetime. HyGain 3750 User's Group - http://groups.yahoo.com/group/HyGain_3750/ http://incolor.inetnebr.com/jshorney http://www.nebraskaghosts.org ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
Re: [Drakelist] TR7 high pitched wine in audio
The first thing I would look at is the filter cap on the DC-DC converter (Power Supply) board in the front right corner of the radio. This capacitor is IMO an always replace for any TR-7. Strange things can happen when it starts to fail, and on a rig that old it most likely is. Replace with a part specified for 105C temperature if possible. There was also an engineering change to add a 470uF axial cap to the +10v rail. This was added by Drake service to any radio that did not have it. Look for it on the bottom side of the chassis, between pins 10 (+10V) and pin 3 (ground) of the DC-DC coverter board connector. 73 -Jim NU0C On Mon, 20 Jan 2014 20:04:55 -0800 (PST), Leon Zebrick wrote: Picked up an early Sr# TR7. It's fine except for a high pitched noise in the audio. It's continuous and not affected by volume control. Not on transmit signal. It's not loud, but noticeable and annoying in headphones. Sounds like one of the oscillators is getting into the audio circuit. Any decoupling mods or improvements related to this? Sr no. Is in the 600 range. Wonder if this is something Drake eventually improved on. Or do I have a problem? Thanks. -- Theres something out of place lets go and poke it with a stick. The Doctor, Amys Choice ___ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
