I sometimes see people chasing a drinks chiller on here and they seem to be like hens teeth. Most domestic fridges are much to small for the purpose of maturing your harvest so, for what it is worth, here is a solution I applied to a large, glass doored freezer and which could be equally applied to a chest freezer which can often be picked up for not much money.
The problem with a freezer is that the highest temperature setting is still to cold for tenderising/hanging venison. Ideally the chiller temperature should be between 1deg.C and 7deg.C.
The solution, get a secondhand upright or chest freezer and from e-bay a ELITECH STC-1000 temperature controller (the one that is 220V with 10 amp rated relays). They cost about £15.
You will need to mount the controller, plus a 13amp. socket outlet into a suitable box. A short length of flex. cable, fitted with a 13 amp. plug is wired into the two 'MAINS INPUT' terminals on the controller. The socket outlet is wired, within the box, to the two 'COOL' terminals of the controller. The 2 metre long, flexible temperature probe which is supplied with the controller is wired into the two 'SENSOR' terminals of the controller.
Job almost done!
Now plug the device you have just assembled into a 13 amp. socket and plug your freezer into the socket you mounted in the device, put the temperature probe in the freezer (the probe is so thin it will simply pass through the door opening and the door seals will not be affected.
Switch on at the wall socket.
This will energise the temperature controller. There are 4 items to set on the controller (and it is easy).
F1 - to set your desired temperature(I would advise +1deg.C)
F2 - to set the temperature switching differential i.e. after the chiller has reached your set temperature and switched off, the temperature in the chiller will now begin to rise and needs to be set to switch back on to recommence chilling. (I would advise 4 deg. which means the chiller will switch back on at 1 + 4 = 5 degrees.
F3 - to set a delay between the chiller compressor switching off and switching back on. (If you don't have a reasonable delay set and have fairly close temperature control such as the 4 degrees variance as described for F2 the compressor will be on and off like the proverbial fiddlers elbow and won't do much for compressor longevity - they don't like it!)
F4 - is for thermostat calibration which you can forget about for this purpose.
Once you have the system up and running put a glass of water in the chiller and let it run for 24 hours, checking to make sure that the water isn't freezing. If it is just tweak the temperature setting by 0.5 degrees until all is well.
The quality of thermal insulation of your chosen freezer will determine how frequently the temperature fluctuates between 1 degree and 5 degrees but the upper temperature is also effected by extended compressor down-time when auto-defrosting is taking place (assuming your freezer has this facility) You will find in all probability that the upper temperature during these auto-defrost periods reaches about 7 deg. C.
Once you have meat in your new chiller the meat will not warm up to the approximate 7 degrees as above, it is only the cooled air which does, and than only for a very short period.
If you take the average temperature in the chiller, using the settings suggested above, to be 4 deg.C and apply this to the recommended 40 deg. C times days for tenderisation you can see that 10 days will give you superbly tender meat. This time can be extended by up to 50% if you prefer greater tenderness. It is a matter of trial and error to suit your taste.
The advantage of using a freezer in this modified form means you can quickly revert to freezer operation by unplugging the device.
A further advantage is being able to re-set the temperature to slightly above 10 deg. C and use the chiller to cool freshly shot game for 12 hours whilst rigor dissapates thus avoiding risk of shortening due to too rapid cooling.
Final note: You could fit the temperature controller into the freezer and wire it internally. If in doubt, contact me and I will explain how; it's not difficult.