 
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
|
|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
65.78.8.172
I have an assortment of Holco H4P 1W 1% metal film resistors. I've seen a recommendation to limit the use of the H4P resistors to voltages no higher than 150VDC. Yay? Nay? Maybe? My most immediate project, and application for them I am considering, is refreshing some bits of a Dynaco FM-3 tube tuner.Thanks!
- SJ
Edits: 09/28/09Follow Ups:
FWIW, I have experienced failures of those Holcos with much less than 150V across them. (I was aware of the potential problem, too.) In one case, the resistor failed with only 45V across it and about 8mA of current, for a dissipation of only 0.36W. If I use them at all, I try to restrict to very low dissipation and voltage, way below the "rating".
Geezz! 45V and 8mA! That's not good at all. Application in tubed gear, as I have planned with my Dynaco FM-3, doesn't sound like a good idea?
- SJ
In my case it was serving as cathode resistor for a tube-based CCS. I thought it was weird, too. In fact, it took me a long time to find the problem, because I did not even suspect the resistor as culprit, at first. Once I did identify the failure, I investigated to see whether some other part might have failed, resulting in a dramatic increase in voltage or current. Couldn't find any evidence for that. Three other Holcos in the same piece of gear and doing similar service (two CCSs per channel in a stereo tube preamp) did not fail. However, I replaced them all with 5W Mills types, way overkill but peace of mind is good. This could have been a freak incident, I admit.
What consumer group or govt agency backs up claims made by these independent manufacturers? I suppose this is a good reason why there has to be mil spec standards. I'd hate to have one of those resistors in a missile.
Well, from the datasheet it would seem that these resistors would work for the Dynaco FM-3 (this tuner tends to run on the warmer side) I'm thinking about using them in at the moment. The reason for my inquiry was some off-datasheet comments I'd seen. Some of the values I'm replacing are 1W, some 1/2W, so I'm within the rating limits of the 1W-rated H4P.
- SJ
I have always made sure that the drop across any given Holco was less than 100 volts. I have used them with a fairly high absolute voltage but with a small drop and they worked just fine. The problem they have is that they cannot take heat. Do not use them as plate load resistors.
___
Long Live Dr.Gizmo
According to Holco's recommendations, the 1/8th watt rated resistor (H8) has 150VDC rating. One-half watt (H4) has 250VDC. Though not stated, I'd imagine that the 1-watt (H4P) has at least 250VDC rating, if not more. Anyhow, check link I found:
Post a Followup:
| FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
||||||||||||||
This post is made possible by the generous support of people like you and our sponsors:
Top of Page ]
[ Contact Us ]
[ Support/Wish List ]
[ Copyright © 2025, Audio Asylum, all rights reserved ]
