PET 6540 ROM operating temperature

John Kaur digitgraph at
Thu Nov 20 01:44:08 CST 2014

My general rule, is if cannot hold your finger on for a count of five, you
need fan directly on it (or sink, Robertson said), & experience has told
me, that one-two years life!!
John Kaur. in AZ where its hot>

On Wed, Nov 19, 2014 at 10:39 PM, John Robertson <pinball at> wrote:

> On 11/19/2014, 5:47 PM, Josh Dersch wrote:
>> Hey all --
>> A quick one -- what's the normal operating temperature for the old MPS6540
>> ROMs used in the original Commodore PETs?  I noticed last night after
>> running mine for ~30 minutes that the ROMs were very hot, to the point of
>> being painful to touch.
>> The machine is running fine as far as I can tell -- though I haven't
>> verified the contents of the ROMs, BASIC runs without any apparent issues.
>> Voltages are normal (just a shade under 5V).
>> I've not experienced ROM chips that run so very hot -- is this normal?
>> Thanks,
>> Josh
>>  A fan is a good idea on older electronics. the cooler they run the
> longer they last. A heat sink epoxied to the top of hot ceramic devices is
> not bad either...
> John :-#)#
> --
> John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
> Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, VideoGames)
> "Old pinballers never die, they just flip out"

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