- Old Capacitors Reading Too Good! - 5 Updates
- CHASE GPR4403 Laboratory Receiver Service manual PLEASE - 2 Updates
| Three Jeeps <jjhudak4@gmail.com>: Jul 06 10:37AM -0700 On Thursday, July 6, 2023 at 11:51:06 AM UTC-4, Dan Green wrote: > vary a lot anyway, but if I have say a 480uF cap which is reading > 640uF, should that be a concern? Does it indicate some underlying > issue with the cap? Yes, higher values indicate a leakage issue. IMHO, capacitor measurement reading should be taken with a grain of salt. Where they occur in the ckt needs to be taken into consideration as well as the age and type of cap. The most often cited usage is in power supplies (both linear and SMPS). As a general rule of thumb, for me, if it is a linear PS, over 20 yo, and there are PS behaviors that suggest a capacitor issue, replace all the electrolytics with equivalent capacitance and slightly higher WVDC if possible. Not worth revisiting that repair later down the road. If one comes across a dead SMPS and it is a capacitor issue, replace them all. It is not worth saving 50 cents just to rebuild it later. I believe a better measurement approach to diagnosing bad caps is a capacitor checker in conjunction with an ESR meter. As I mentioned, these are my guidelines/approaches. I am sure other ppl have theirs and may disagree with me. I'll just say to each their own. Good luck |
| HW <none@no.no>: Jul 06 11:25PM +0200 On Thu, 06 Jul 2023 16:51:01 +0100, Dan Green <dhg99908@hotmail.se> wrote: >Is it advisable to change old electrolytics which are reading a >capacitance considerably higher than their stated value? Yes, definitely. If you measure the cap with a "simple" meter, like a multimeter, a failed or failing capacitor can "trick" the instrument to read high. |
| Dan Green <dhg99908@hotmail.se>: Jul 06 10:51PM +0100 >Yes, definitely. >If you measure the cap with a "simple" meter, like a multimeter, a >failed or failing capacitor can "trick" the instrument to read high. No, I'm talking about bespoke ESR/capacitance meters here. |
| Phil Allison <pallison49@gmail.com>: Jul 06 11:32PM -0700 Dan Green wrote: --------------------------- > vary a lot anyway, but if I have say a 480uF cap which is reading > 640uF, should that be a concern? Does it indicate some underlying > issue with the cap? ** Usually, the first warning of electro cap failure is when the ESR reading is higher than normal. This indicates most of the electrolyte has been lost by evaporation. Significant loss of capacitance starts later. Increasing capacitance indicates a different condition, where the max voltage goes down in reverse to the increased C value. Usually this only accompanies many years of non use. ..... Phil |
| Arie de Muijnck <noreply@ademu.com>: Jul 07 09:08AM +0200 On 2023-07-06 17:51, Dan Green wrote: > vary a lot anyway, but if I have say a 480uF cap which is reading > 640uF, should that be a concern? Does it indicate some underlying > issue with the cap? If you use a real C / ESR meter, it may indicate the isolation layer has thinned over time. In that case, reforming with a small current to the proper voltage could repair the electrolytic. However, it also indicates the age - and replacement is certainly better. Arie |
| Tony <83d72b796d91c68f5fa0209d60bf1173@example.com>: Jul 06 09:30PM Looks like these threads are years old so this will probably never be read! I designed the receiver. There is no service manual, unless one was done after I left the company. The receiver was calibrated automatically by computer over the rs 232 port before the units were shipped. The calibration points were stored in eprom. Depending on the year of manufacture there was a backup battery or 1 farad cap as backup. As the original spec was 10 years receiver life most receivers have now probably died. The cal software ran on a BBC micro. Any programming info is long gone. -- For full context, visit https://www.electrondepot.com/repair/chase-gpr4403-laboratory-receiver-service-manual-please-29513-.htm |
| John Robertson <jrr@flippers.com>: Jul 06 04:05PM -0700 On 2023/07/06 2:30 p.m., Tony wrote: > As the original spec was 10 years receiver life most receivers have now > probably died. The cal software ran on a BBC micro. Any programming info > is long gone. Talk about planned obsolescence! So the receiver calibration might change over time and there is absolutely no way to fix this as there is no calibration program left anywhere. I/m assuming if anything was changed in the receiver that it would then need calibration... And people wonder why I like fixing electronic toys prior to the 2000s! Stuff after 2000 is not nearly as fixable - too many one-off or customer parts. Then there is the question of who owns the device they bought. As an example one brand of pinball games shuts the game down if it is operated on 50 or 60 Hertz and that is different than the line frequency (60/50Hz) that the game was originally set up for. John :-#(# -- (Please post followups or tech inquiries to the USENET newsgroup) John's Jukes Ltd. #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3 (604)872-5757 (Pinballs, Jukes, Video Games) www.flippers.com "Old pinballers never die, they just flip out." |
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