Question about "frog" type Seal dry mount press

[beatricethecat]

Hi all - I work for a school and we have a very big, older "frog" type dry mount press. It worked for years just fine then something shorted and melted one of the wire nuts inside. Just got around to fixing that and giving it a new power cord and plug (rated for 20A - its 2000W). Powers up fine, gets hot, turns off when at temp (used a thermometer to set the temp knob) but the whole top of the unit gets very hot and I can't recall if this is normal? Not overheated, just very hot. It is designed like a big heatsink + the excess heat needs to go somewhere. But just in case I wanted to ask if anyone has a similar press and if so, does the top get hot? The only other odd thing is bulb in the left "eye" of the frog lights up but its very faint. I tried different bulbs with the same result. Thanks in advance for any help!

 

[ic-racer]

Left bulb, red? That one blinks for timing the press.

 

[beatricethecat]

Left bulb, red? That one blinks for timing the press.

Yes, it is red. I always thought it stayed lit to indicate the press was on, I don't remember it ever blinking, but that's awesome if it's supposed to. Then again, maybe it never lit up properly as the press was a hand-me-down from our papermaking studio. We spent quite awhile buffing the platen back to clean.

 

[ic-racer]

This picture is about 15 year old, but as I recall the device circled is the blinker circuit.

 

[ic-racer]

 

[koraks]

as I recall the device circled is the blinker circuit.

The only recognizable part in the circled section appears to be a common glass fuse.

I expect that the blinker section is the bit right next to the circled section:

The vertical pin would likely engage with the clamp handle being pressed down. I guess that the blinking is done with a bimetal contact heating up and breaking the circuit, then re-connecting as it cools down. It's easy to see how this could get stuck in either permanently closed or open position due to fouling etc.

Given the construction I don't see how the top would not get hot, so yes, I'd expect this to be normal behavior. There's no significant insulation anywhere.

 

[ic-racer]

The blinker circuit, which is indeed shaped like a common glass fuse, uses a heated strip to make/break the circuit to the left lamp. The frequency is about 1/sec. This device has a patent from the 1930s.

The thermostat, held to the top casting with four machine screws, is a commonly replaced item and B&H used to sell them at the time I was refurbishing that press.

 

[koraks]

Okay, gotcha.

 

[ic-racer]

For blinker replacement look for something similar to Littelfuse FS126-60, thought it might need to be mounted outside the electrical cavity due to thermal considerations (operating temp. of the device: -20 to 60 C). Because, to answer your original question, the top plate does get pretty hot during operation.

 

[ic-racer]

The flasher could be re-located to be mounted with the microswitch which actuates the flasher circuit on the side of the handle.

 

[xkaes]

That looks like a heavily-used 350 model from the 1960's. I'm surprised it still works.

 

[beatricethecat]

Thanks everyone for your replies!

Especially ic-racer, I really, really appreciate the photos and super helpful info!! I realized the relay wasn't functioning properly - the metal was bent in a way that once the lid was closed it wasn't turning the micro switch on. I was able to bend it back and now the red light turns on when it's closed! But no blinking, so the blinker circut-fuselike-thingy must not work anymore. I found one on eBay for $10 so I might try that out first before modifying it with a newer kind, but I understand what you are saying about not putting it in where the previous one was as it might melt. Did you sandblast the one you were refurbishing? It looks so clean and nice!