For a Heathkit VTVM, need 1% resistors at least 1/2 watt, 7 and 9 megaohms.
Any idea where to get them, Mouser and Digikey no have.

TY
Scott

 

What's wrong with 1 Mohm resistors in series?

 

Second hit in Google search: Caddoc precision high resistance/voltage resistors; upper left icon. The Sales pulldown menu gives links for direct sales and distributors.

 

For a Heathkit VTVM, need 1% resistors at least 1/2 watt, 7 and 9 megaohms.
Any idea where to get them, Mouser and Digikey no have.

TY
Scott

Why do you need at least half watt?
It would take at least 2,100V to dissipate 1/2W into a 9Mohm resistor.

 

They probably won;t fit. Try these guys: http://store.ohmcraft.com/

At least they sell onesies.

 

Why do you need at least half watt?
It would take at least 2,100V to dissipate 1/2W into a 9Mohm resistor.{/quote]

With a 1000 V input (guessing) and a 2x safety factor, that isn't to bad.

I had to buy a 1 Meg 200 W resistor once and on the other side of the scale a 0.5 ohm adjustable resistor rated at 1000 W and I did buy a few 400 M resistor onec.

 

With a 1000 V input (guessing) and a 2x safety factor, that isn't to bad.

When I googled "Heathkit VTVM" I saw a bunch of VOMs that only measured up to 15VDC.

 

When I googled "Heathkit VTVM" I saw a bunch of VOMs that only measured up to 15VDC.

They are reference resistors for the vacuum tubes. I think 1/2 watt is recommended to limit heat extremes of "properly" sized resistors and limit heat effects on accuracy.

 

They are reference resistors for the vacuum tubes. I think 1/2 watt is recommended to limit heat extremes of "properly" sized resistors and limit heat effects on accuracy.

Got it, thanks!

 

The 7 and 9 megaohm are part of the main voltage divider reference. The existing ones have drifted a little high, which throws off
voltage readings. Ohmcraft might be a possibility if they will sell one off. TY Keepitsimple

 

https://www.arrow.com/en/products/c...tm_medium=buynow&utm_campaign=octopart#page-1

http://www.digikey.com/product-deta...3423?WT.z_cid=ref_octopart_dkc_buynow&site=us
(use 2 parallel)

1M are really common so if it was me I would do a PCB with 1M SM resistors and fast on tabs or something to avoid the high MOQs

 

Here's a search at Mouser that gets pretty close. 9.09M 1/2 Watt, 6.81M .4W, in stock. Monkey around with the filters for other close ones. Lots more 1/8Watts. Maybe parallel a couple. Vishay is a good go-to for things like this.