We experienced heat issues with our DR 680 mkI at Greyfox. It was about 95 degrees, but "feels like 102" on weatherunderground.
What happened is tough to describe and maybe kindms can fill it in for us:
We were recording 6 channels, all Phantom powered, with AKG 460 B/ck22, C414XLS/ST's, and ck61 naiant actives. About 45 minutes into the first 1 hour set,, 2 of the channels (3/4) started showing a constant level at about -20dB while the other four channels were moving with the music.Plugged in the headphones, solo'd to 3/4 and all we could hear was a bump-bump-bump, almost heartbeat sounding tone ABOVE the music. After listening a bit and handing the phones to kindms who agreed that the tone was present, we started planning on what to do when the set ended. (BTW, we use ecocharge dual 6/12 V newly refurbished by kindms batteries- and they have been flawle3ss for us for years)
We had a lunch break and decided to use the 414's with his HDP-2 and use channels 1/2 and 5/6 only (ck22's & ck61's). we also listened to the recording and it seemed there was no adverse affects, no added noise etc from what we could tell using earbuds on my computer.
We swapped out SD cards for one which had no data on it (deleted on computer and formatted in 680). We then went and reconfigured our set up to include the HDP-2 as above.
We still wound up with the constant levels and bumping almost 20 minutes into the set. It was about 6 PM by that time and the heat was INCREDIBLE on the hill. We touched the 680 and it was ON FIRE. we pulled it out of the bag, placed it in a cooler area and made sure to power down between sets.
When the sun went down, we had none of those issues. Truthfully, I have yet to critically listen to the offending sets as they were not the music I really wanted to listen to later (Sierra Hull and Mr.Sun).
All the other sets we recorded with the 680 have zero negative effects. Kindms tells me there is a thread, maybe this one, which indicates others have had heat issues.
When I get to listen to the Sierra Hull I will report back to this thread. We bought the deck used, so there is no warranty that I am aware of, so we will not be calling customer service, especially as it is probably our issue with heat/power and not theirs.