Topics

Suspect Parts


nm0s_qrp <ai9e_qrp@...>
 

The tolerance for these ceramic disk capacitors is -20%, +80%, so  50% high is within their spec.  These parts are applied in circuit functions where their value, dissipation, and leakage are not critical.  Unless a component s is faulty, like your experience with C9, the parts supplied with the kit are entirely satisfactory for their intended use.  
As far as counterfeit semiconductors go, the 2N3019 transistors used in the Ozark Patrol were, until recently, old stock from 20+ year old inventory, and not suspect.  Since that supply has dried up, we now use parts obtained from a reputable supplier.
Speaking from personal experience, and having obtained a LOT of components from different sources, the biggest problem with counterfeit parts so far encountered were the 2N7000 transistors purchased for the Cricket kit.  The first batch of 'no-name' parts purchased proved to meet all published specs, but had far lower RF gain than parts from ON Semi or ST.  But, RF gain is NOT a specified parameter for these parts, so the still met 'spec', but were unusable for the kit.  So, I have a box of a couple thousand of them waiting for an application where RF gain is not critical.

73 Dave NM0S


Jerome Wysocki
 

Curt, please keep us posted on your progress with the Ozark Patrol receiver when finished. I checked all resistors before using them here and all were ok. I have problems with regeneration being way too unstable, frequently on this receiver. I made a post several months earlier on this topic, but got no responses. Maybe I have a similar problem with bad caps.

If anyone is interested, I can discuss this topic in a new thread. I've made some notable progress on my problem, and I do believe the problem is fixable.
... Jerry Wysocki, KC9JXE


Curt
 

More experiences with problematic parts.

Building the Ozark Patrol yesterday, three of the caps in the kit (C2, C8, and C9) are obviously and easily recognized from you know where..  I always test these and as expected C2 & C8 were about 50% high of marked value with discharge ten times my stock.  C9 was open.  As usual, tossed them in waste and replaced with my own stock.  If they had tested nominally good, not sure if could trust the reliability.

 

Had the same issue with the .01 and .1 caps in the Hilltopper kit, and single-band transceiver kit from another vendor.  Not all were bad but enough to have no confidence in the reliability of the finished kit using the supplied parts.  Once again replaced all with my own stock.  That has become my default approach to these cheapest of parts.

Active components identified with transistor and Fet numbers must be tested too.  I have encountered "Fets" that were audio transistors, "RF" transistors that were actually AF or non-functioning devices.  Years ago I assumed that parts identified as new parts were as labeled and functional.  Never tested new parts.  Now I test everything I can before installing it.  So far haven't been bitten by a counterfeit IC, but they are surely out there waiting.

73, Curt


Dale Putnam
 

Very well put, Curt, and I echo the same test results. 
Cost of repairs are higher.. but they only need be done ONCE.

Have a great day,

Dale - WC7S in Wy

"Actions speak louder than words"



From: main@4SQRP.groups.io <main@4SQRP.groups.io> on behalf of Curt via Groups.Io <rhulett1@...>
Sent: Saturday, August 17, 2019 2:03 PM
To: main@4SQRP.groups.io <main@4SQRP.groups.io>
Subject: [4SQRP] Suspect Parts
 
For awhile, substandard parts, (small value ceramic capacitors and transistors in particular), have been sold for very low prices on the auction site.  Had encountered these in very cheap kits from the same site and always considered it getting what was paid for.  Routine testing of these components was necessary to avoid building a brick, usually replacing the bad parts with parts from a vendor like Mouser, Digikey, Newark, etc.  Sometimes wholesale replacement was easier than testing as even with testing, the life of the suspect capacitors is unknown.  An audio transistor relabeled as an RF transistor or RF FET can be frustrating.

More recently, have been encountering these same substandard parts in kits sold by qrp clubs and small us vendors. Most have likely always relied on the quality of the provided components, and didn't bother testing components before installation. Those days are over. My two most recently purchased kits had substandard 0.1 uf ceramic capacitors as tested.  When I test a component and find it 1/2 the labeled value with ten times the loss I don't trust it at all.

Curt KB5JO


Curt
 

For awhile, substandard parts, (small value ceramic capacitors and transistors in particular), have been sold for very low prices on the auction site.  Had encountered these in very cheap kits from the same site and always considered it getting what was paid for.  Routine testing of these components was necessary to avoid building a brick, usually replacing the bad parts with parts from a vendor like Mouser, Digikey, Newark, etc.  Sometimes wholesale replacement was easier than testing as even with testing, the life of the suspect capacitors is unknown.  An audio transistor relabeled as an RF transistor or RF FET can be frustrating.

More recently, have been encountering these same substandard parts in kits sold by qrp clubs and small us vendors. Most have likely always relied on the quality of the provided components, and didn't bother testing components before installation. Those days are over. My two most recently purchased kits had substandard 0.1 uf ceramic capacitors as tested.  When I test a component and find it 1/2 the labeled value with ten times the loss I don't trust it at all.

Curt KB5JO