Racal RA1795 - UK Vintage Radio Repair and Restoration Discussion Forum

mickm3for · 14th Aug 2020, 8:49 pm

Hi this racal rx has a heat sensitive ic (rm1019-a) and the heat from the power unit causes the radio to malfunction after 30 mins .5 second blast of frezer and its back. Run radio with panell hinged up away from the heat of the power unit and it runs normaly, as this ic is not available thought abont fitting a peltier thermoelectric cooler + a transformer to run it. Has anyone any experience of these devices, a normal fan would only blow the hot air around in the sealed case, the psu iis in a sealed metal box this after 3 hours is hot around 102F and the ic in question is only 4 inches away thanks in advance Mick

Jon_G4MDC · 15th Aug 2020, 10:25 am

Peltier chip doesn't remove heat it only creates a hot side and a cold side.

You need somewhere for the heat to go so you would need to mount the peltier cold side to the IC and the hot side to a heat sink of some sort.

Chrispy57 · 16th Aug 2020, 5:54 pm

Hi Mick,
have you been able to work out what the function of that particular IC might be, and why it should now be running hot after many years of normal operation? I understand that it is not replaceable due to its scarcity, but you may be lucky and find that perhaps another component may be the culprit and actually be a replaceable item.

Failing that, perhaps try a heatsink attached to the IC itself as that may bring the local temperature down below the threshold of the fault condition without appreciably affecting the overall temperature inside the sealed case?

Finally, could something else be causing the PSU to now overheat, do you know the current draws of each supply and if they are in spec?

Good luck with the trouble-shooting, looks like a nice receiver.

Cheers
Chris

14th Aug 2020, 8:49 pm	#1
mickm3for Heptode Join Date: May 2015 Location: Chatham, Kent, UK. Posts: 964	Racal RA1795 Hi this racal rx has a heat sensitive ic (rm1019-a) and the heat from the power unit causes the radio to malfunction after 30 mins .5 second blast of frezer and its back. Run radio with panell hinged up away from the heat of the power unit and it runs normaly, as this ic is not available thought abont fitting a peltier thermoelectric cooler + a transformer to run it. Has anyone any experience of these devices, a normal fan would only blow the hot air around in the sealed case, the psu iis in a sealed metal box this after 3 hours is hot around 102F and the ic in question is only 4 inches away thanks in advance Mick

15th Aug 2020, 10:25 am	#2
Jon_G4MDC Nonode Join Date: Nov 2015 Location: Welwyn Garden City, Hertfordshire, UK. Posts: 2,015	Re: Racal RA1795 Peltier chip doesn't remove heat it only creates a hot side and a cold side. You need somewhere for the heat to go so you would need to mount the peltier cold side to the IC and the hot side to a heat sink of some sort.

16th Aug 2020, 5:54 pm	#3
Chrispy57 Hexode Join Date: Mar 2020 Location: Rochdale, Greater Manchester, UK. Posts: 452	Re: Racal RA1795 Hi Mick, have you been able to work out what the function of that particular IC might be, and why it should now be running hot after many years of normal operation? I understand that it is not replaceable due to its scarcity, but you may be lucky and find that perhaps another component may be the culprit and actually be a replaceable item. Failing that, perhaps try a heatsink attached to the IC itself as that may bring the local temperature down below the threshold of the fault condition without appreciably affecting the overall temperature inside the sealed case? Finally, could something else be causing the PSU to now overheat, do you know the current draws of each supply and if they are in spec? Good luck with the trouble-shooting, looks like a nice receiver. Cheers Chris