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The PHILCO Phorum > Philco Radio Discussions > Philco Electronic Restoration > 7z4 tube in place of 7y4 are they compatible
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Derek38

12-18-2019, 09:29 PM
In my 41-608 I just noticed that someone substituted a 7z4 tube for a 7y4 will that cause a problem?

Ron Ramirez

12-18-2019, 09:52 PM
Yes - the 7Z4 has a higher heater current (0.9A) than the 7Y4 (0.5A). This will stress the power transformer. You don't want to stress a nearly 80 year old power transformer if you can avoid it.
The PHILCO Phorum > Philco Radio Discussions > Philco Electronic Restoration > 7z4 tube in place of 7y4 are they compatible